From b77d09d0df8cef5d88e3da75e7c57f881872d0ce Mon Sep 17 00:00:00 2001
From: Brock Mendel <jbrockmendel@gmail.com>
Date: Mon, 2 Oct 2017 08:56:24 -0700
Subject: [PATCH 01/32] Move tseries.frequencies funcs up to tslibs.frequencies

---
 pandas/_libs/period.pyx             |  13 +-
 pandas/_libs/tslib.pyx              |  24 +--
 pandas/_libs/tslibs/frequencies.pxd |   6 +
 pandas/_libs/tslibs/frequencies.pyx | 264 +++++++++++++++++++++++++++-
 pandas/tseries/frequencies.py       | 240 +------------------------
 5 files changed, 284 insertions(+), 263 deletions(-)

diff --git a/pandas/_libs/period.pyx b/pandas/_libs/period.pyx
index 49353f7b0491c..ce8c7e8578d8f 100644
--- a/pandas/_libs/period.pyx
+++ b/pandas/_libs/period.pyx
@@ -38,7 +38,10 @@ from tslibs.timezones cimport (
     is_utc, is_tzlocal, get_utcoffset, _get_dst_info, maybe_get_tz)
 from tslib cimport _nat_scalar_rules
 
-from tslibs.frequencies cimport get_freq_code
+from tslibs.frequencies cimport (
+    get_freq_code, get_base_alias, get_to_timestamp_base, _get_freq_str,
+    _get_rule_month)
+from tslibs.frequencies import _MONTH_NUMBERS
 
 from pandas.tseries import offsets
 from pandas.core.tools.datetimes import parse_time_string
@@ -683,7 +686,7 @@ cdef class _Period(object):
 
         if isinstance(freq, (int, tuple)):
             code, stride = get_freq_code(freq)
-            freq = frequencies._get_freq_str(code, stride)
+            freq = _get_freq_str(code, stride)
 
         freq = frequencies.to_offset(freq)
 
@@ -742,7 +745,7 @@ cdef class _Period(object):
             raise IncompatibleFrequency(msg.format(self.freqstr))
         elif isinstance(other, offsets.DateOffset):
             freqstr = other.rule_code
-            base = frequencies.get_base_alias(freqstr)
+            base = get_base_alias(freqstr)
             if base == self.freq.rule_code:
                 ordinal = self.ordinal + other.n
                 return Period(ordinal=ordinal, freq=self.freq)
@@ -860,7 +863,7 @@ cdef class _Period(object):
 
         if freq is None:
             base, mult = get_freq_code(self.freq)
-            freq = frequencies.get_to_timestamp_base(base)
+            freq = get_to_timestamp_base(base)
 
         base, mult = get_freq_code(freq)
         val = self.asfreq(freq, how)
@@ -1249,7 +1252,7 @@ def _quarter_to_myear(year, quarter, freq):
         if quarter <= 0 or quarter > 4:
             raise ValueError('Quarter must be 1 <= q <= 4')
 
-        mnum = tslib._MONTH_NUMBERS[tslib._get_rule_month(freq)] + 1
+        mnum = _MONTH_NUMBERS[_get_rule_month(freq)] + 1
         month = (mnum + (quarter - 1) * 3) % 12 + 1
         if month > mnum:
             year -= 1
diff --git a/pandas/_libs/tslib.pyx b/pandas/_libs/tslib.pyx
index ec12611ae7f02..6fdaf5f0e0deb 100644
--- a/pandas/_libs/tslib.pyx
+++ b/pandas/_libs/tslib.pyx
@@ -111,7 +111,8 @@ from tslibs.timezones import (  # noqa
     _unbox_utcoffsets,
     _dateutil_gettz
     )
-
+from tslibs.frequencies cimport _get_rule_month
+from tslibs.frequencies import _get_rule_month  # noqa
 
 cdef inline object create_timestamp_from_ts(
         int64_t value, pandas_datetimestruct dts,
@@ -2117,27 +2118,6 @@ _MONTH_NUMBERS = {k: i for i, k in enumerate(_MONTHS)}
 _MONTH_ALIASES = {(k + 1): v for k, v in enumerate(_MONTHS)}
 
 
-cpdef object _get_rule_month(object source, object default='DEC'):
-    """
-    Return starting month of given freq, default is December.
-
-    Example
-    -------
-    >>> _get_rule_month('D')
-    'DEC'
-
-    >>> _get_rule_month('A-JAN')
-    'JAN'
-    """
-    if hasattr(source, 'freqstr'):
-        source = source.freqstr
-    source = source.upper()
-    if '-' not in source:
-        return default
-    else:
-        return source.split('-')[1]
-
-
 cpdef array_with_unit_to_datetime(ndarray values, unit, errors='coerce'):
     """
     convert the ndarray according to the unit
diff --git a/pandas/_libs/tslibs/frequencies.pxd b/pandas/_libs/tslibs/frequencies.pxd
index 974eb4ab45df0..b5bb3cd9dd596 100644
--- a/pandas/_libs/tslibs/frequencies.pxd
+++ b/pandas/_libs/tslibs/frequencies.pxd
@@ -1,4 +1,10 @@
 # -*- coding: utf-8 -*-
 # cython: profile=False
 
+cpdef object _get_rule_month(object source, object default=*)
+
 cpdef get_freq_code(freqstr)
+cpdef get_freq(freq)
+cpdef get_base_alias(freqstr)
+cpdef get_to_timestamp_base(base)
+cpdef _get_freq_str(base, mult=*)
diff --git a/pandas/_libs/tslibs/frequencies.pyx b/pandas/_libs/tslibs/frequencies.pyx
index f7889d76abbc7..4973887e9f4e5 100644
--- a/pandas/_libs/tslibs/frequencies.pyx
+++ b/pandas/_libs/tslibs/frequencies.pyx
@@ -6,9 +6,32 @@ cimport cython
 
 import numpy as np
 cimport numpy as np
+from numpy cimport int64_t
 np.import_array()
 
-from util cimport is_integer_object
+from util cimport is_integer_object, is_string_object
+
+
+#----------------------------------------------------------------------
+cpdef object _get_rule_month(object source, object default='DEC'):
+    """
+    Return starting month of given freq, default is December.
+
+    Example
+    -------
+    >>> _get_rule_month('D')
+    'DEC'
+
+    >>> _get_rule_month('A-JAN')
+    'JAN'
+    """
+    if hasattr(source, 'freqstr'):
+        source = source.freqstr
+    source = source.upper()
+    if '-' not in source:
+        return default
+    else:
+        return source.split('-')[1]
 
 
 cpdef get_freq_code(freqstr):
@@ -202,3 +225,242 @@ cpdef _period_str_to_code(freqstr):
         return _period_code_map[freqstr]
     except KeyError:
         raise ValueError(_INVALID_FREQ_ERROR.format(freqstr))
+
+
+cpdef _get_freq_str(base, mult=1):
+    code = _reverse_period_code_map.get(base)
+    if mult == 1:
+        return code
+    return str(mult) + code
+
+
+cpdef get_base_alias(freqstr):
+    """
+    Returns the base frequency alias, e.g., '5D' -> 'D'
+    """
+    return _base_and_stride(freqstr)[0]
+
+
+class FreqGroup(object):
+    FR_ANN = 1000
+    FR_QTR = 2000
+    FR_MTH = 3000
+    FR_WK = 4000
+    FR_BUS = 5000
+    FR_DAY = 6000
+    FR_HR = 7000
+    FR_MIN = 8000
+    FR_SEC = 9000
+    FR_MS = 10000
+    FR_US = 11000
+    FR_NS = 12000
+
+
+cpdef get_to_timestamp_base(base):
+    """
+    Return frequency code group used for base of to_timestamp against
+    frequency code.
+
+    Example
+    -------
+    # Return day freq code against longer freq than day
+    >>> get_to_timestamp_base(get_freq_code('D')[0])
+    6000
+    >>> get_to_timestamp_base(get_freq_code('W')[0])
+    6000
+    >>> get_to_timestamp_base(get_freq_code('M')[0])
+    6000
+
+    # Return second freq code against hour between second
+    >>> get_to_timestamp_base(get_freq_code('H')[0])
+    9000
+    >>> get_to_timestamp_base(get_freq_code('S')[0])
+    9000
+    """
+    if base < FreqGroup.FR_BUS:
+        return FreqGroup.FR_DAY
+    if FreqGroup.FR_HR <= base <= FreqGroup.FR_SEC:
+        return FreqGroup.FR_SEC
+    return base
+
+
+cpdef get_freq(freq):
+    """
+    Return frequency code of given frequency str.
+    If input is not string, return input as it is.
+
+    Example
+    -------
+    >>> get_freq('A')
+    1000
+
+    >>> get_freq('3A')
+    1000
+    """
+    if is_string_object(freq):
+        base, mult = get_freq_code(freq)
+        freq = base
+    return freq
+
+
+#----------------------------------------------------------------------
+# Frequency comparison
+
+def is_subperiod(source, target):
+    """
+    Returns True if downsampling is possible between source and target
+    frequencies
+
+    Parameters
+    ----------
+    source : string
+        Frequency converting from
+    target : string
+        Frequency converting to
+
+    Returns
+    -------
+    is_subperiod : boolean
+    """
+
+    if target is None or source is None:
+        return False
+    source = _maybe_coerce_freq(source)
+    target = _maybe_coerce_freq(target)
+
+    if _is_annual(target):
+        if _is_quarterly(source):
+            return _quarter_months_conform(_get_rule_month(source),
+                                           _get_rule_month(target))
+        return source in ['D', 'C', 'B', 'M', 'H', 'T', 'S', 'L', 'U', 'N']
+    elif _is_quarterly(target):
+        return source in ['D', 'C', 'B', 'M', 'H', 'T', 'S', 'L', 'U', 'N']
+    elif _is_monthly(target):
+        return source in ['D', 'C', 'B', 'H', 'T', 'S', 'L', 'U', 'N']
+    elif _is_weekly(target):
+        return source in [target, 'D', 'C', 'B', 'H', 'T', 'S', 'L', 'U', 'N']
+    elif target == 'B':
+        return source in ['B', 'H', 'T', 'S', 'L', 'U', 'N']
+    elif target == 'C':
+        return source in ['C', 'H', 'T', 'S', 'L', 'U', 'N']
+    elif target == 'D':
+        return source in ['D', 'H', 'T', 'S', 'L', 'U', 'N']
+    elif target == 'H':
+        return source in ['H', 'T', 'S', 'L', 'U', 'N']
+    elif target == 'T':
+        return source in ['T', 'S', 'L', 'U', 'N']
+    elif target == 'S':
+        return source in ['S', 'L', 'U', 'N']
+    elif target == 'L':
+        return source in ['L', 'U', 'N']
+    elif target == 'U':
+        return source in ['U', 'N']
+    elif target == 'N':
+        return source in ['N']
+
+
+def is_superperiod(source, target):
+    """
+    Returns True if upsampling is possible between source and target
+    frequencies
+
+    Parameters
+    ----------
+    source : string
+        Frequency converting from
+    target : string
+        Frequency converting to
+
+    Returns
+    -------
+    is_superperiod : boolean
+    """
+    if target is None or source is None:
+        return False
+    source = _maybe_coerce_freq(source)
+    target = _maybe_coerce_freq(target)
+
+    if _is_annual(source):
+        if _is_annual(target):
+            return _get_rule_month(source) == _get_rule_month(target)
+
+        if _is_quarterly(target):
+            smonth = _get_rule_month(source)
+            tmonth = _get_rule_month(target)
+            return _quarter_months_conform(smonth, tmonth)
+        return target in ['D', 'C', 'B', 'M', 'H', 'T', 'S', 'L', 'U', 'N']
+    elif _is_quarterly(source):
+        return target in ['D', 'C', 'B', 'M', 'H', 'T', 'S', 'L', 'U', 'N']
+    elif _is_monthly(source):
+        return target in ['D', 'C', 'B', 'H', 'T', 'S', 'L', 'U', 'N']
+    elif _is_weekly(source):
+        return target in [source, 'D', 'C', 'B', 'H', 'T', 'S', 'L', 'U', 'N']
+    elif source == 'B':
+        return target in ['D', 'C', 'B', 'H', 'T', 'S', 'L', 'U', 'N']
+    elif source == 'C':
+        return target in ['D', 'C', 'B', 'H', 'T', 'S', 'L', 'U', 'N']
+    elif source == 'D':
+        return target in ['D', 'C', 'B', 'H', 'T', 'S', 'L', 'U', 'N']
+    elif source == 'H':
+        return target in ['H', 'T', 'S', 'L', 'U', 'N']
+    elif source == 'T':
+        return target in ['T', 'S', 'L', 'U', 'N']
+    elif source == 'S':
+        return target in ['S', 'L', 'U', 'N']
+    elif source == 'L':
+        return target in ['L', 'U', 'N']
+    elif source == 'U':
+        return target in ['U', 'N']
+    elif source == 'N':
+        return target in ['N']
+
+
+def _maybe_coerce_freq(code):
+    """ we might need to coerce a code to a rule_code
+    and uppercase it
+
+    Parameters
+    ----------
+    source : string
+        Frequency converting from
+
+    Returns
+    -------
+    string code
+    """
+    assert code is not None
+    if getattr(code, '_typ', None) == 'dateoffset':
+        # i.e. isinstance(code, ABCDateOffset):
+        code = code.rule_code
+    return code.upper()
+
+
+_MONTHS = ['JAN', 'FEB', 'MAR', 'APR', 'MAY', 'JUN', 'JUL',
+           'AUG', 'SEP', 'OCT', 'NOV', 'DEC']
+_MONTH_NUMBERS = {k: i for i, k in enumerate(_MONTHS)}
+
+
+def _quarter_months_conform(source, target):
+    snum = _MONTH_NUMBERS[source]
+    tnum = _MONTH_NUMBERS[target]
+    return snum % 3 == tnum % 3
+
+
+def _is_annual(rule):
+    rule = rule.upper()
+    return rule == 'A' or rule.startswith('A-')
+
+
+def _is_quarterly(rule):
+    rule = rule.upper()
+    return rule == 'Q' or rule.startswith('Q-') or rule.startswith('BQ')
+
+
+def _is_monthly(rule):
+    rule = rule.upper()
+    return rule == 'M' or rule == 'BM'
+
+
+def _is_weekly(rule):
+    rule = rule.upper()
+    return rule == 'W' or rule.startswith('W-')
diff --git a/pandas/tseries/frequencies.py b/pandas/tseries/frequencies.py
index 085a3a784557b..2f876bea4ad00 100644
--- a/pandas/tseries/frequencies.py
+++ b/pandas/tseries/frequencies.py
@@ -23,25 +23,14 @@
 from pandas._libs.tslibs.frequencies import (  # noqa
     get_freq_code, _base_and_stride, _period_str_to_code,
     _INVALID_FREQ_ERROR, opattern, _lite_rule_alias, _dont_uppercase,
-    _period_code_map, _reverse_period_code_map)
+    _period_code_map, _reverse_period_code_map, get_base_alias,
+    FreqGroup, get_to_timestamp_base, get_freq, _get_freq_str,
+    _maybe_coerce_freq, is_subperiod, is_superperiod,
+    _is_annual, _is_quarterly, _is_monthly, _is_weekly,
+    _quarter_months_conform, _get_rule_month)
 from pytz import AmbiguousTimeError
 
 
-class FreqGroup(object):
-    FR_ANN = 1000
-    FR_QTR = 2000
-    FR_MTH = 3000
-    FR_WK = 4000
-    FR_BUS = 5000
-    FR_DAY = 6000
-    FR_HR = 7000
-    FR_MIN = 8000
-    FR_SEC = 9000
-    FR_MS = 10000
-    FR_US = 11000
-    FR_NS = 12000
-
-
 RESO_NS = 0
 RESO_US = 1
 RESO_MS = 2
@@ -229,34 +218,6 @@ def get_stride_from_decimal(cls, value, freq):
             return cls.get_stride_from_decimal(next_value, next_name)
 
 
-def get_to_timestamp_base(base):
-    """
-    Return frequency code group used for base of to_timestamp against
-    frequency code.
-
-    Example
-    -------
-    # Return day freq code against longer freq than day
-    >>> get_to_timestamp_base(get_freq_code('D')[0])
-    6000
-    >>> get_to_timestamp_base(get_freq_code('W')[0])
-    6000
-    >>> get_to_timestamp_base(get_freq_code('M')[0])
-    6000
-
-    # Return second freq code against hour between second
-    >>> get_to_timestamp_base(get_freq_code('H')[0])
-    9000
-    >>> get_to_timestamp_base(get_freq_code('S')[0])
-    9000
-    """
-    if base < FreqGroup.FR_BUS:
-        return FreqGroup.FR_DAY
-    if FreqGroup.FR_HR <= base <= FreqGroup.FR_SEC:
-        return FreqGroup.FR_SEC
-    return base
-
-
 def get_freq_group(freq):
     """
     Return frequency code group of given frequency str or offset.
@@ -282,32 +243,6 @@ def get_freq_group(freq):
     return (freq // 1000) * 1000
 
 
-def get_freq(freq):
-    """
-    Return frequency code of given frequency str.
-    If input is not string, return input as it is.
-
-    Example
-    -------
-    >>> get_freq('A')
-    1000
-
-    >>> get_freq('3A')
-    1000
-    """
-    if isinstance(freq, compat.string_types):
-        base, mult = get_freq_code(freq)
-        freq = base
-    return freq
-
-
-def _get_freq_str(base, mult=1):
-    code = _reverse_period_code_map.get(base)
-    if mult == 1:
-        return code
-    return str(mult) + code
-
-
 # ---------------------------------------------------------------------
 # Offset names ("time rules") and related functions
 
@@ -498,13 +433,6 @@ def to_offset(freq):
     return delta
 
 
-def get_base_alias(freqstr):
-    """
-    Returns the base frequency alias, e.g., '5D' -> 'D'
-    """
-    return _base_and_stride(freqstr)[0]
-
-
 def get_offset(name):
     """
     Return DateOffset object associated with rule name
@@ -878,164 +806,6 @@ def _maybe_add_count(base, count):
         return base
 
 
-def _maybe_coerce_freq(code):
-    """ we might need to coerce a code to a rule_code
-    and uppercase it
-
-    Parameters
-    ----------
-    source : string
-        Frequency converting from
-
-    Returns
-    -------
-    string code
-    """
-
-    assert code is not None
-    if isinstance(code, offsets.DateOffset):
-        code = code.rule_code
-    return code.upper()
-
-
-def is_subperiod(source, target):
-    """
-    Returns True if downsampling is possible between source and target
-    frequencies
-
-    Parameters
-    ----------
-    source : string
-        Frequency converting from
-    target : string
-        Frequency converting to
-
-    Returns
-    -------
-    is_subperiod : boolean
-    """
-
-    if target is None or source is None:
-        return False
-    source = _maybe_coerce_freq(source)
-    target = _maybe_coerce_freq(target)
-
-    if _is_annual(target):
-        if _is_quarterly(source):
-            return _quarter_months_conform(_get_rule_month(source),
-                                           _get_rule_month(target))
-        return source in ['D', 'C', 'B', 'M', 'H', 'T', 'S', 'L', 'U', 'N']
-    elif _is_quarterly(target):
-        return source in ['D', 'C', 'B', 'M', 'H', 'T', 'S', 'L', 'U', 'N']
-    elif _is_monthly(target):
-        return source in ['D', 'C', 'B', 'H', 'T', 'S', 'L', 'U', 'N']
-    elif _is_weekly(target):
-        return source in [target, 'D', 'C', 'B', 'H', 'T', 'S', 'L', 'U', 'N']
-    elif target == 'B':
-        return source in ['B', 'H', 'T', 'S', 'L', 'U', 'N']
-    elif target == 'C':
-        return source in ['C', 'H', 'T', 'S', 'L', 'U', 'N']
-    elif target == 'D':
-        return source in ['D', 'H', 'T', 'S', 'L', 'U', 'N']
-    elif target == 'H':
-        return source in ['H', 'T', 'S', 'L', 'U', 'N']
-    elif target == 'T':
-        return source in ['T', 'S', 'L', 'U', 'N']
-    elif target == 'S':
-        return source in ['S', 'L', 'U', 'N']
-    elif target == 'L':
-        return source in ['L', 'U', 'N']
-    elif target == 'U':
-        return source in ['U', 'N']
-    elif target == 'N':
-        return source in ['N']
-
-
-def is_superperiod(source, target):
-    """
-    Returns True if upsampling is possible between source and target
-    frequencies
-
-    Parameters
-    ----------
-    source : string
-        Frequency converting from
-    target : string
-        Frequency converting to
-
-    Returns
-    -------
-    is_superperiod : boolean
-    """
-    if target is None or source is None:
-        return False
-    source = _maybe_coerce_freq(source)
-    target = _maybe_coerce_freq(target)
-
-    if _is_annual(source):
-        if _is_annual(target):
-            return _get_rule_month(source) == _get_rule_month(target)
-
-        if _is_quarterly(target):
-            smonth = _get_rule_month(source)
-            tmonth = _get_rule_month(target)
-            return _quarter_months_conform(smonth, tmonth)
-        return target in ['D', 'C', 'B', 'M', 'H', 'T', 'S', 'L', 'U', 'N']
-    elif _is_quarterly(source):
-        return target in ['D', 'C', 'B', 'M', 'H', 'T', 'S', 'L', 'U', 'N']
-    elif _is_monthly(source):
-        return target in ['D', 'C', 'B', 'H', 'T', 'S', 'L', 'U', 'N']
-    elif _is_weekly(source):
-        return target in [source, 'D', 'C', 'B', 'H', 'T', 'S', 'L', 'U', 'N']
-    elif source == 'B':
-        return target in ['D', 'C', 'B', 'H', 'T', 'S', 'L', 'U', 'N']
-    elif source == 'C':
-        return target in ['D', 'C', 'B', 'H', 'T', 'S', 'L', 'U', 'N']
-    elif source == 'D':
-        return target in ['D', 'C', 'B', 'H', 'T', 'S', 'L', 'U', 'N']
-    elif source == 'H':
-        return target in ['H', 'T', 'S', 'L', 'U', 'N']
-    elif source == 'T':
-        return target in ['T', 'S', 'L', 'U', 'N']
-    elif source == 'S':
-        return target in ['S', 'L', 'U', 'N']
-    elif source == 'L':
-        return target in ['L', 'U', 'N']
-    elif source == 'U':
-        return target in ['U', 'N']
-    elif source == 'N':
-        return target in ['N']
-
-
-_get_rule_month = tslib._get_rule_month
-
-
-def _is_annual(rule):
-    rule = rule.upper()
-    return rule == 'A' or rule.startswith('A-')
-
-
-def _quarter_months_conform(source, target):
-    snum = _month_numbers[source]
-    tnum = _month_numbers[target]
-    return snum % 3 == tnum % 3
-
-
-def _is_quarterly(rule):
-    rule = rule.upper()
-    return rule == 'Q' or rule.startswith('Q-') or rule.startswith('BQ')
-
-
-def _is_monthly(rule):
-    rule = rule.upper()
-    return rule == 'M' or rule == 'BM'
-
-
-def _is_weekly(rule):
-    rule = rule.upper()
-    return rule == 'W' or rule.startswith('W-')
-
-
 DAYS = ['MON', 'TUE', 'WED', 'THU', 'FRI', 'SAT', 'SUN']
 
 MONTHS = tslib._MONTHS

From b5198f368d9cbb6c4798fea37e1b4dba2fa1c1cb Mon Sep 17 00:00:00 2001
From: Brock Mendel <jbrockmendel@gmail.com>
Date: Thu, 19 Oct 2017 21:32:37 -0700
Subject: [PATCH 02/32] more specific noqa, try to fix incorrect flake warning

---
 pandas/tseries/frequencies.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pandas/tseries/frequencies.py b/pandas/tseries/frequencies.py
index 2ac49873452e7..9fdedf506fdef 100644
--- a/pandas/tseries/frequencies.py
+++ b/pandas/tseries/frequencies.py
@@ -21,7 +21,7 @@
 
 from pandas._libs import lib, tslib
 from pandas._libs.tslib import Timedelta
-from pandas._libs.tslibs.frequencies import (  # noqa
+from pandas._libs.tslibs.frequencies import (  # noqa:F811
     get_freq_code, _base_and_stride, _period_str_to_code,
     _INVALID_FREQ_ERROR, opattern, _lite_rule_alias, _dont_uppercase,
     _period_code_map, _reverse_period_code_map, get_base_alias,

From 3bfbdf1dbf577715463a8ab883500e1d303a4bb2 Mon Sep 17 00:00:00 2001
From: Brock Mendel <jbrockmendel@gmail.com>
Date: Tue, 24 Oct 2017 09:34:09 -0700
Subject: [PATCH 03/32] disable flake8 false-positives

---
 pandas/tseries/frequencies.py | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/pandas/tseries/frequencies.py b/pandas/tseries/frequencies.py
index 9fdedf506fdef..19c3ecdc8db01 100644
--- a/pandas/tseries/frequencies.py
+++ b/pandas/tseries/frequencies.py
@@ -19,9 +19,9 @@
 from pandas.util._decorators import cache_readonly, deprecate_kwarg
 import pandas.tseries.offsets as offsets
 
-from pandas._libs import lib, tslib
+from pandas._libs import tslib
 from pandas._libs.tslib import Timedelta
-from pandas._libs.tslibs.frequencies import (  # noqa:F811
+from pandas._libs.tslibs.frequencies import (  # noqa:F401
     get_freq_code, _base_and_stride, _period_str_to_code,
     _INVALID_FREQ_ERROR, opattern, _lite_rule_alias, _dont_uppercase,
     _period_code_map, _reverse_period_code_map, get_base_alias,
@@ -138,7 +138,7 @@ def get_freq_group(cls, resostr):
         """
         return get_freq_group(cls.get_freq(resostr))
 
-    @classmethod
+    @classmethod  # noqa:F811  # Disable flake8 false-positive
     def get_freq(cls, resostr):
         """
         Return frequency str against resolution str.
@@ -582,7 +582,7 @@ def is_unique(self):
     def is_unique_asi8(self):
         return len(self.deltas_asi8) == 1
 
-    def get_freq(self):
+    def get_freq(self):  # noqa:F811  # Disable flake8 false-positive
         if not self.is_monotonic or not self.index.is_unique:
             return None
 
@@ -632,7 +632,7 @@ def fields(self):
 
     @cache_readonly
     def rep_stamp(self):
-        return lib.Timestamp(self.values[0])
+        return tslib.Timestamp(self.values[0])
 
     def month_position_check(self):
         # TODO: cythonize this, very slow

From 74258c098e6190b9e12ebaf686329cdcde783dee Mon Sep 17 00:00:00 2001
From: Brock Mendel <jbrockmendel@gmail.com>
Date: Wed, 1 Nov 2017 09:25:09 -0700
Subject: [PATCH 04/32] flake8 fixup

---
 pandas/_libs/tslibs/frequencies.pyx | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/pandas/_libs/tslibs/frequencies.pyx b/pandas/_libs/tslibs/frequencies.pyx
index 92adbea76acf7..004f8e74eff9d 100644
--- a/pandas/_libs/tslibs/frequencies.pyx
+++ b/pandas/_libs/tslibs/frequencies.pyx
@@ -12,7 +12,7 @@ np.import_array()
 from util cimport is_integer_object, is_string_object
 
 
-#----------------------------------------------------------------------
+# ----------------------------------------------------------------------
 cpdef object _get_rule_month(object source, object default='DEC'):
     """
     Return starting month of given freq, default is December.
@@ -304,7 +304,7 @@ cpdef get_freq(freq):
     return freq
 
 
-#----------------------------------------------------------------------
+# ----------------------------------------------------------------------
 # Frequency comparison
 
 def is_subperiod(source, target):

From 823db82ea8d3eecec0d6254f67509836fc428f77 Mon Sep 17 00:00:00 2001
From: Brock Mendel <jbrockmendel@gmail.com>
Date: Wed, 1 Nov 2017 09:30:32 -0700
Subject: [PATCH 05/32] consolidate constants near top of file

---
 pandas/_libs/tslibs/frequencies.pyx | 54 ++++++++++++++---------------
 1 file changed, 27 insertions(+), 27 deletions(-)

diff --git a/pandas/_libs/tslibs/frequencies.pyx b/pandas/_libs/tslibs/frequencies.pyx
index 004f8e74eff9d..402ccfa506617 100644
--- a/pandas/_libs/tslibs/frequencies.pyx
+++ b/pandas/_libs/tslibs/frequencies.pyx
@@ -11,31 +11,13 @@ np.import_array()
 
 from util cimport is_integer_object, is_string_object
 
-
-# ----------------------------------------------------------------------
-cpdef object _get_rule_month(object source, object default='DEC'):
-    """
-    Return starting month of given freq, default is December.
-
-    Example
-    -------
-    >>> _get_rule_month('D')
-    'DEC'
-
-    >>> _get_rule_month('A-JAN')
-    'JAN'
-    """
-    if hasattr(source, 'freqstr'):
-        source = source.freqstr
-    source = source.upper()
-    if '-' not in source:
-        return default
-    else:
-        return source.split('-')[1]
-
 # ----------------------------------------------------------------------
 # Constants
 
+_MONTHS = ['JAN', 'FEB', 'MAR', 'APR', 'MAY', 'JUN', 'JUL',
+           'AUG', 'SEP', 'OCT', 'NOV', 'DEC']
+_MONTH_NUMBERS = {k: i for i, k in enumerate(_MONTHS)}
+
 # hack to handle WOM-1MON
 opattern = re.compile(
     r'([\-]?\d*|[\-]?\d*\.\d*)\s*([A-Za-z]+([\-][\dA-Za-z\-]+)?)'
@@ -436,11 +418,6 @@ def _maybe_coerce_freq(code):
     return code.upper()
 
 
-_MONTHS = ['JAN', 'FEB', 'MAR', 'APR', 'MAY', 'JUN', 'JUL',
-           'AUG', 'SEP', 'OCT', 'NOV', 'DEC']
-_MONTH_NUMBERS = {k: i for i, k in enumerate(_MONTHS)}
-
-
 def _quarter_months_conform(source, target):
     snum = _MONTH_NUMBERS[source]
     tnum = _MONTH_NUMBERS[target]
@@ -465,3 +442,26 @@ def _is_monthly(rule):
 def _is_weekly(rule):
     rule = rule.upper()
     return rule == 'W' or rule.startswith('W-')
+
+
+# ----------------------------------------------------------------------
+
+cpdef object _get_rule_month(object source, object default='DEC'):
+    """
+    Return starting month of given freq, default is December.
+
+    Example
+    -------
+    >>> _get_rule_month('D')
+    'DEC'
+
+    >>> _get_rule_month('A-JAN')
+    'JAN'
+    """
+    if hasattr(source, 'freqstr'):
+        source = source.freqstr
+    source = source.upper()
+    if '-' not in source:
+        return default
+    else:
+        return source.split('-')[1]

From 551f0471cd768354b0cb444c67d350b31aabf3b6 Mon Sep 17 00:00:00 2001
From: Brock Mendel <jbrockmendel@gmail.com>
Date: Thu, 2 Nov 2017 17:14:43 -0700
Subject: [PATCH 06/32] remove unused variable

---
 pandas/tseries/frequencies.py | 1 -
 1 file changed, 1 deletion(-)

diff --git a/pandas/tseries/frequencies.py b/pandas/tseries/frequencies.py
index 5201721145f8d..3f2877359beb0 100644
--- a/pandas/tseries/frequencies.py
+++ b/pandas/tseries/frequencies.py
@@ -765,7 +765,6 @@ def _maybe_add_count(base, count):
 DAYS = ['MON', 'TUE', 'WED', 'THU', 'FRI', 'SAT', 'SUN']
 
 MONTHS = tslib._MONTHS
-_month_numbers = tslib._MONTH_NUMBERS
 _month_aliases = tslib._MONTH_ALIASES
 _weekday_rule_aliases = dict((k, v) for k, v in enumerate(DAYS))
 

From 2a2155eab4bd95f4fe996db786e578f18bd662de Mon Sep 17 00:00:00 2001
From: Brock Mendel <jbrockmendel@gmail.com>
Date: Fri, 10 Nov 2017 07:44:01 -0800
Subject: [PATCH 07/32] update imports per reviewer request

---
 pandas/_libs/tslib.pyx                    |  1 -
 pandas/tests/scalar/test_period_asfreq.py |  2 +-
 pandas/tests/tseries/test_frequencies.py  | 69 ++++++++++++-----------
 pandas/tests/tseries/test_offsets.py      |  6 +-
 pandas/tseries/frequencies.py             | 16 +++---
 5 files changed, 49 insertions(+), 45 deletions(-)

diff --git a/pandas/_libs/tslib.pyx b/pandas/_libs/tslib.pyx
index eed3f49975343..c9e7317eedd0c 100644
--- a/pandas/_libs/tslib.pyx
+++ b/pandas/_libs/tslib.pyx
@@ -90,7 +90,6 @@ from tslibs.timezones cimport (
     treat_tz_as_dateutil, treat_tz_as_pytz,
     get_timezone, get_utcoffset, maybe_get_tz,
     get_dst_info)
-from tslibs.frequencies cimport _get_rule_month
 from tslibs.fields import (
     get_date_name_field, get_start_end_field, get_date_field,
     build_field_sarray)
diff --git a/pandas/tests/scalar/test_period_asfreq.py b/pandas/tests/scalar/test_period_asfreq.py
index 32cea60c333b7..c7fbe61488fcc 100644
--- a/pandas/tests/scalar/test_period_asfreq.py
+++ b/pandas/tests/scalar/test_period_asfreq.py
@@ -1,7 +1,7 @@
 import pandas as pd
 from pandas import Period, offsets
 from pandas.util import testing as tm
-from pandas.tseries.frequencies import _period_code_map
+from pandas._libs.tslibs.frequencies import _period_code_map
 
 
 class TestFreqConversion(object):
diff --git a/pandas/tests/tseries/test_frequencies.py b/pandas/tests/tseries/test_frequencies.py
index 745f3ef2ec5cb..450e42f8cccf6 100644
--- a/pandas/tests/tseries/test_frequencies.py
+++ b/pandas/tests/tseries/test_frequencies.py
@@ -7,6 +7,9 @@
 from pandas import (Index, DatetimeIndex, Timestamp, Series,
                     date_range, period_range)
 
+from pandas._libs.tslibs.frequencies import (_period_code_map, _get_rule_month,
+                                             _period_str_to_code)
+
 import pandas.tseries.frequencies as frequencies
 from pandas.core.tools.datetimes import to_datetime
 
@@ -284,84 +287,84 @@ def test_rule_aliases():
 
 
 def test_get_rule_month():
-    result = frequencies._get_rule_month('W')
+    result = _get_rule_month('W')
     assert (result == 'DEC')
-    result = frequencies._get_rule_month(offsets.Week())
+    result = _get_rule_month(offsets.Week())
     assert (result == 'DEC')
 
-    result = frequencies._get_rule_month('D')
+    result = _get_rule_month('D')
     assert (result == 'DEC')
-    result = frequencies._get_rule_month(offsets.Day())
+    result = _get_rule_month(offsets.Day())
     assert (result == 'DEC')
 
-    result = frequencies._get_rule_month('Q')
+    result = _get_rule_month('Q')
     assert (result == 'DEC')
-    result = frequencies._get_rule_month(offsets.QuarterEnd(startingMonth=12))
+    result = _get_rule_month(offsets.QuarterEnd(startingMonth=12))
     print(result == 'DEC')
 
-    result = frequencies._get_rule_month('Q-JAN')
+    result = _get_rule_month('Q-JAN')
     assert (result == 'JAN')
-    result = frequencies._get_rule_month(offsets.QuarterEnd(startingMonth=1))
+    result = _get_rule_month(offsets.QuarterEnd(startingMonth=1))
     assert (result == 'JAN')
 
-    result = frequencies._get_rule_month('A-DEC')
+    result = _get_rule_month('A-DEC')
     assert (result == 'DEC')
-    result = frequencies._get_rule_month('Y-DEC')
+    result = _get_rule_month('Y-DEC')
     assert (result == 'DEC')
-    result = frequencies._get_rule_month(offsets.YearEnd())
+    result = _get_rule_month(offsets.YearEnd())
     assert (result == 'DEC')
 
-    result = frequencies._get_rule_month('A-MAY')
+    result = _get_rule_month('A-MAY')
     assert (result == 'MAY')
-    result = frequencies._get_rule_month('Y-MAY')
+    result = _get_rule_month('Y-MAY')
     assert (result == 'MAY')
-    result = frequencies._get_rule_month(offsets.YearEnd(month=5))
+    result = _get_rule_month(offsets.YearEnd(month=5))
     assert (result == 'MAY')
 
 
 def test_period_str_to_code():
-    assert (frequencies._period_str_to_code('A') == 1000)
-    assert (frequencies._period_str_to_code('A-DEC') == 1000)
-    assert (frequencies._period_str_to_code('A-JAN') == 1001)
-    assert (frequencies._period_str_to_code('Y') == 1000)
-    assert (frequencies._period_str_to_code('Y-DEC') == 1000)
-    assert (frequencies._period_str_to_code('Y-JAN') == 1001)
+    assert (_period_str_to_code('A') == 1000)
+    assert (_period_str_to_code('A-DEC') == 1000)
+    assert (_period_str_to_code('A-JAN') == 1001)
+    assert (_period_str_to_code('Y') == 1000)
+    assert (_period_str_to_code('Y-DEC') == 1000)
+    assert (_period_str_to_code('Y-JAN') == 1001)
 
-    assert (frequencies._period_str_to_code('Q') == 2000)
-    assert (frequencies._period_str_to_code('Q-DEC') == 2000)
-    assert (frequencies._period_str_to_code('Q-FEB') == 2002)
+    assert (_period_str_to_code('Q') == 2000)
+    assert (_period_str_to_code('Q-DEC') == 2000)
+    assert (_period_str_to_code('Q-FEB') == 2002)
 
     def _assert_depr(freq, expected, aliases):
         assert isinstance(aliases, list)
-        assert (frequencies._period_str_to_code(freq) == expected)
+        assert (_period_str_to_code(freq) == expected)
 
         msg = frequencies._INVALID_FREQ_ERROR
         for alias in aliases:
             with tm.assert_raises_regex(ValueError, msg):
-                frequencies._period_str_to_code(alias)
+                _period_str_to_code(alias)
 
     _assert_depr("M", 3000, ["MTH", "MONTH", "MONTHLY"])
 
-    assert (frequencies._period_str_to_code('W') == 4000)
-    assert (frequencies._period_str_to_code('W-SUN') == 4000)
-    assert (frequencies._period_str_to_code('W-FRI') == 4005)
+    assert (_period_str_to_code('W') == 4000)
+    assert (_period_str_to_code('W-SUN') == 4000)
+    assert (_period_str_to_code('W-FRI') == 4005)
 
     _assert_depr("B", 5000, ["BUS", "BUSINESS", "BUSINESSLY", "WEEKDAY"])
     _assert_depr("D", 6000, ["DAY", "DLY", "DAILY"])
     _assert_depr("H", 7000, ["HR", "HOUR", "HRLY", "HOURLY"])
 
     _assert_depr("T", 8000, ["minute", "MINUTE", "MINUTELY"])
-    assert (frequencies._period_str_to_code('Min') == 8000)
+    assert (_period_str_to_code('Min') == 8000)
 
     _assert_depr("S", 9000, ["sec", "SEC", "SECOND", "SECONDLY"])
     _assert_depr("L", 10000, ["MILLISECOND", "MILLISECONDLY"])
-    assert (frequencies._period_str_to_code('ms') == 10000)
+    assert (_period_str_to_code('ms') == 10000)
 
     _assert_depr("U", 11000, ["MICROSECOND", "MICROSECONDLY"])
-    assert (frequencies._period_str_to_code('US') == 11000)
+    assert (_period_str_to_code('US') == 11000)
 
     _assert_depr("N", 12000, ["NANOSECOND", "NANOSECONDLY"])
-    assert (frequencies._period_str_to_code('NS') == 12000)
+    assert (_period_str_to_code('NS') == 12000)
 
 
 class TestFrequencyCode(object):
@@ -379,7 +382,7 @@ def test_freq_code(self):
         assert frequencies.get_freq('W-MON') == 4001
         assert frequencies.get_freq('W-FRI') == 4005
 
-        for freqstr, code in compat.iteritems(frequencies._period_code_map):
+        for freqstr, code in compat.iteritems(_period_code_map):
             result = frequencies.get_freq(freqstr)
             assert result == code
 
diff --git a/pandas/tests/tseries/test_offsets.py b/pandas/tests/tseries/test_offsets.py
index 4fd3bba01602f..85d03b417db7b 100644
--- a/pandas/tests/tseries/test_offsets.py
+++ b/pandas/tests/tseries/test_offsets.py
@@ -12,8 +12,10 @@
 from pandas.compat.numpy import np_datetime64_compat
 
 from pandas.core.series import Series
-from pandas.tseries.frequencies import (_offset_map, get_freq_code,
-                                        _get_freq_str, _INVALID_FREQ_ERROR,
+
+from pandas._libs.tslibs.frequencies import get_freq_code, _get_freq_str
+from pandas.tseries.frequencies import (_offset_map,
+                                        _INVALID_FREQ_ERROR,
                                         get_offset, get_standard_freq)
 from pandas.core.indexes.datetimes import (
     _to_m8, DatetimeIndex, _daterange_cache)
diff --git a/pandas/tseries/frequencies.py b/pandas/tseries/frequencies.py
index 3f2877359beb0..d08cd674d355e 100644
--- a/pandas/tseries/frequencies.py
+++ b/pandas/tseries/frequencies.py
@@ -21,14 +21,14 @@
 
 from pandas._libs import tslib
 from pandas._libs.tslib import Timedelta
-from pandas._libs.tslibs.frequencies import (  # noqa:F401
-    get_freq_code, _base_and_stride, _period_str_to_code,
-    _INVALID_FREQ_ERROR, opattern, _lite_rule_alias, _dont_uppercase,
-    _period_code_map, _reverse_period_code_map, get_base_alias,
-    FreqGroup, get_to_timestamp_base, get_freq, _get_freq_str,
-    _maybe_coerce_freq, is_subperiod, is_superperiod,
-    _is_annual, _is_quarterly, _is_monthly, _is_weekly,
-    _quarter_months_conform, _get_rule_month)
+from pandas._libs.tslibs.frequencies import (
+    get_freq_code, _base_and_stride,
+    _INVALID_FREQ_ERROR, opattern,
+    _lite_rule_alias, _dont_uppercase)
+from pandas._libs.tslibs.frequencies import (  # noqa
+    get_freq, get_base_alias, get_to_timestamp_base,
+    FreqGroup,
+    is_subperiod, is_superperiod)
 from pytz import AmbiguousTimeError
 
 

From 4192c0db99ab96d925b25290e445d6d58f77b218 Mon Sep 17 00:00:00 2001
From: Brock Mendel <jbrockmendel@gmail.com>
Date: Fri, 10 Nov 2017 08:36:18 -0800
Subject: [PATCH 08/32] trim namespace using libfreqs

---
 pandas/tseries/frequencies.py | 30 ++++++++++++++----------------
 1 file changed, 14 insertions(+), 16 deletions(-)

diff --git a/pandas/tseries/frequencies.py b/pandas/tseries/frequencies.py
index d08cd674d355e..34cbbe983c3be 100644
--- a/pandas/tseries/frequencies.py
+++ b/pandas/tseries/frequencies.py
@@ -21,11 +21,9 @@
 
 from pandas._libs import tslib
 from pandas._libs.tslib import Timedelta
-from pandas._libs.tslibs.frequencies import (
-    get_freq_code, _base_and_stride,
-    _INVALID_FREQ_ERROR, opattern,
-    _lite_rule_alias, _dont_uppercase)
-from pandas._libs.tslibs.frequencies import (  # noqa
+import pandas._libs.tslibs.frequencies as libfreqs
+from pandas._libs.tslibs.frequencies import get_freq_code
+from pandas._libs.tslibs.frequencies import (  # noqa, semi-public API
     get_freq, get_base_alias, get_to_timestamp_base,
     FreqGroup,
     is_subperiod, is_superperiod)
@@ -333,7 +331,7 @@ def to_offset(freq):
         stride = freq[1]
         if isinstance(stride, compat.string_types):
             name, stride = stride, name
-        name, _ = _base_and_stride(name)
+        name, _ = libfreqs._base_and_stride(name)
         delta = get_offset(name) * stride
 
     elif isinstance(freq, timedelta):
@@ -350,13 +348,13 @@ def to_offset(freq):
                     else:
                         delta = delta + offset
         except Exception:
-            raise ValueError(_INVALID_FREQ_ERROR.format(freq))
+            raise ValueError(libfreqs._INVALID_FREQ_ERROR.format(freq))
 
     else:
         delta = None
         stride_sign = None
         try:
-            splitted = re.split(opattern, freq)
+            splitted = re.split(libfreqs.opattern, freq)
             if splitted[-1] != '' and not splitted[-1].isspace():
                 # the last element must be blank
                 raise ValueError('last element must be blank')
@@ -364,7 +362,7 @@ def to_offset(freq):
                                          splitted[2::4]):
                 if sep != '' and not sep.isspace():
                     raise ValueError('separator must be spaces')
-                prefix = _lite_rule_alias.get(name) or name
+                prefix = libfreqs._lite_rule_alias.get(name) or name
                 if stride_sign is None:
                     stride_sign = -1 if stride.startswith('-') else 1
                 if not stride:
@@ -381,10 +379,10 @@ def to_offset(freq):
                 else:
                     delta = delta + offset
         except Exception:
-            raise ValueError(_INVALID_FREQ_ERROR.format(freq))
+            raise ValueError(libfreqs._INVALID_FREQ_ERROR.format(freq))
 
     if delta is None:
-        raise ValueError(_INVALID_FREQ_ERROR.format(freq))
+        raise ValueError(libfreqs._INVALID_FREQ_ERROR.format(freq))
 
     return delta
 
@@ -397,12 +395,12 @@ def get_offset(name):
     --------
     get_offset('EOM') --> BMonthEnd(1)
     """
-    if name not in _dont_uppercase:
+    if name not in libfreqs._dont_uppercase:
         name = name.upper()
-        name = _lite_rule_alias.get(name, name)
-        name = _lite_rule_alias.get(name.lower(), name)
+        name = libfreqs._lite_rule_alias.get(name, name)
+        name = libfreqs._lite_rule_alias.get(name.lower(), name)
     else:
-        name = _lite_rule_alias.get(name, name)
+        name = libfreqs._lite_rule_alias.get(name, name)
 
     if name not in _offset_map:
         try:
@@ -413,7 +411,7 @@ def get_offset(name):
             offset = klass._from_name(*split[1:])
         except (ValueError, TypeError, KeyError):
             # bad prefix or suffix
-            raise ValueError(_INVALID_FREQ_ERROR.format(name))
+            raise ValueError(libfreqs._INVALID_FREQ_ERROR.format(name))
         # cache
         _offset_map[name] = offset
     # do not return cache because it's mutable

From 21e13dc8fbd00c88a37379a334f8666c2c39876d Mon Sep 17 00:00:00 2001
From: Brock Mendel <jbrockmendel@gmail.com>
Date: Fri, 10 Nov 2017 11:49:04 -0800
Subject: [PATCH 09/32] fix import

---
 pandas/tests/tseries/test_frequencies.py | 7 ++++---
 pandas/tests/tseries/test_offsets.py     | 4 ++--
 2 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/pandas/tests/tseries/test_frequencies.py b/pandas/tests/tseries/test_frequencies.py
index 450e42f8cccf6..7fe29187b23f5 100644
--- a/pandas/tests/tseries/test_frequencies.py
+++ b/pandas/tests/tseries/test_frequencies.py
@@ -8,7 +8,8 @@
                     date_range, period_range)
 
 from pandas._libs.tslibs.frequencies import (_period_code_map, _get_rule_month,
-                                             _period_str_to_code)
+                                             _period_str_to_code,
+                                             _INVALID_FREQ_ERROR)
 
 import pandas.tseries.frequencies as frequencies
 from pandas.core.tools.datetimes import to_datetime
@@ -338,7 +339,7 @@ def _assert_depr(freq, expected, aliases):
         assert isinstance(aliases, list)
         assert (_period_str_to_code(freq) == expected)
 
-        msg = frequencies._INVALID_FREQ_ERROR
+        msg = _INVALID_FREQ_ERROR
         for alias in aliases:
             with tm.assert_raises_regex(ValueError, msg):
                 _period_str_to_code(alias)
@@ -881,7 +882,7 @@ def test_legacy_offset_warnings(self):
                  'WOM@4THU', 'WOM@1FRI', 'WOM@2FRI', 'WOM@3FRI',
                  'WOM@4FRI']
 
-        msg = frequencies._INVALID_FREQ_ERROR
+        msg = _INVALID_FREQ_ERROR
         for freq in freqs:
             with tm.assert_raises_regex(ValueError, msg):
                 frequencies.get_offset(freq)
diff --git a/pandas/tests/tseries/test_offsets.py b/pandas/tests/tseries/test_offsets.py
index 85d03b417db7b..9cb1e37b2f8d5 100644
--- a/pandas/tests/tseries/test_offsets.py
+++ b/pandas/tests/tseries/test_offsets.py
@@ -13,9 +13,9 @@
 
 from pandas.core.series import Series
 
-from pandas._libs.tslibs.frequencies import get_freq_code, _get_freq_str
+from pandas._libs.tslibs.frequencies import (get_freq_code, _get_freq_str,
+                                             _INVALID_FREQ_ERROR)
 from pandas.tseries.frequencies import (_offset_map,
-                                        _INVALID_FREQ_ERROR,
                                         get_offset, get_standard_freq)
 from pandas.core.indexes.datetimes import (
     _to_m8, DatetimeIndex, _daterange_cache)

From 67dbfe211f03783fe5dbf3eb1253f105c79dfe36 Mon Sep 17 00:00:00 2001
From: Brock Mendel <jbrockmendel@gmail.com>
Date: Fri, 10 Nov 2017 15:18:00 -0800
Subject: [PATCH 10/32] update imports

---
 pandas/tests/indexes/datetimes/test_ops.py  | 2 +-
 pandas/tests/indexes/period/test_tools.py   | 2 +-
 pandas/tests/indexes/timedeltas/test_ops.py | 2 +-
 pandas/tests/scalar/test_period.py          | 4 ++--
 pandas/tests/scalar/test_period_asfreq.py   | 6 +++---
 pandas/tests/scalar/test_timestamp.py       | 4 ++--
 6 files changed, 10 insertions(+), 10 deletions(-)

diff --git a/pandas/tests/indexes/datetimes/test_ops.py b/pandas/tests/indexes/datetimes/test_ops.py
index 9e4f8d979ca99..cedafa96a36b6 100644
--- a/pandas/tests/indexes/datetimes/test_ops.py
+++ b/pandas/tests/indexes/datetimes/test_ops.py
@@ -160,7 +160,7 @@ def test_round(self):
             tm.assert_index_equal(rng.round(freq='H'), expected_rng)
             assert elt.round(freq='H') == expected_elt
 
-            msg = pd.tseries.frequencies._INVALID_FREQ_ERROR
+            msg = pd._libs.tslibs.frequencies._INVALID_FREQ_ERROR
             with tm.assert_raises_regex(ValueError, msg):
                 rng.round(freq='foo')
             with tm.assert_raises_regex(ValueError, msg):
diff --git a/pandas/tests/indexes/period/test_tools.py b/pandas/tests/indexes/period/test_tools.py
index 074678164e6f9..0e65b4c300d47 100644
--- a/pandas/tests/indexes/period/test_tools.py
+++ b/pandas/tests/indexes/period/test_tools.py
@@ -367,7 +367,7 @@ def test_to_period_monthish(self):
         prng = rng.to_period()
         assert prng.freq == 'M'
 
-        msg = pd.tseries.frequencies._INVALID_FREQ_ERROR
+        msg = pd._libs.tslibs.frequencies._INVALID_FREQ_ERROR
         with tm.assert_raises_regex(ValueError, msg):
             date_range('01-Jan-2012', periods=8, freq='EOM')
 
diff --git a/pandas/tests/indexes/timedeltas/test_ops.py b/pandas/tests/indexes/timedeltas/test_ops.py
index 67238665a2e8a..6732fc2aa1ca1 100644
--- a/pandas/tests/indexes/timedeltas/test_ops.py
+++ b/pandas/tests/indexes/timedeltas/test_ops.py
@@ -114,7 +114,7 @@ def test_round(self):
         tm.assert_index_equal(td.round(freq='H'), expected_rng)
         assert elt.round(freq='H') == expected_elt
 
-        msg = pd.tseries.frequencies._INVALID_FREQ_ERROR
+        msg = pd._libs.tslibs.frequencies._INVALID_FREQ_ERROR
         with tm.assert_raises_regex(ValueError, msg):
             td.round(freq='foo')
         with tm.assert_raises_regex(ValueError, msg):
diff --git a/pandas/tests/scalar/test_period.py b/pandas/tests/scalar/test_period.py
index 28d85c52604d9..d2962c94a2821 100644
--- a/pandas/tests/scalar/test_period.py
+++ b/pandas/tests/scalar/test_period.py
@@ -513,7 +513,7 @@ def test_period_deprecated_freq(self):
                  "U": ["MICROSECOND", "MICROSECONDLY", "microsecond"],
                  "N": ["NANOSECOND", "NANOSECONDLY", "nanosecond"]}
 
-        msg = pd.tseries.frequencies._INVALID_FREQ_ERROR
+        msg = pd._libs.tslibs.frequencies._INVALID_FREQ_ERROR
         for exp, freqs in iteritems(cases):
             for freq in freqs:
                 with tm.assert_raises_regex(ValueError, msg):
@@ -757,7 +757,7 @@ def test_properties_weekly_legacy(self):
         exp = Period(freq='W', year=2012, month=2, day=1)
         assert exp.days_in_month == 29
 
-        msg = pd.tseries.frequencies._INVALID_FREQ_ERROR
+        msg = pd._libs.tslibs.frequencies._INVALID_FREQ_ERROR
         with tm.assert_raises_regex(ValueError, msg):
             Period(freq='WK', year=2007, month=1, day=7)
 
diff --git a/pandas/tests/scalar/test_period_asfreq.py b/pandas/tests/scalar/test_period_asfreq.py
index c7fbe61488fcc..295209930d435 100644
--- a/pandas/tests/scalar/test_period_asfreq.py
+++ b/pandas/tests/scalar/test_period_asfreq.py
@@ -293,13 +293,13 @@ def test_conv_weekly(self):
 
         assert ival_W.asfreq('W') == ival_W
 
-        msg = pd.tseries.frequencies._INVALID_FREQ_ERROR
+        msg = pd._libs.tslibs.frequencies._INVALID_FREQ_ERROR
         with tm.assert_raises_regex(ValueError, msg):
             ival_W.asfreq('WK')
 
     def test_conv_weekly_legacy(self):
         # frequency conversion tests: from Weekly Frequency
-        msg = pd.tseries.frequencies._INVALID_FREQ_ERROR
+        msg = pd._libs.tslibs.frequencies._INVALID_FREQ_ERROR
         with tm.assert_raises_regex(ValueError, msg):
             Period(freq='WK', year=2007, month=1, day=1)
 
@@ -706,7 +706,7 @@ def test_asfreq_MS(self):
 
         assert initial.asfreq(freq="M", how="S") == Period('2013-01', 'M')
 
-        msg = pd.tseries.frequencies._INVALID_FREQ_ERROR
+        msg = pd._libs.tslibs._INVALID_FREQ_ERROR
         with tm.assert_raises_regex(ValueError, msg):
             initial.asfreq(freq="MS", how="S")
 
diff --git a/pandas/tests/scalar/test_timestamp.py b/pandas/tests/scalar/test_timestamp.py
index 4cd9a2fadeb32..08ef15936363e 100644
--- a/pandas/tests/scalar/test_timestamp.py
+++ b/pandas/tests/scalar/test_timestamp.py
@@ -18,6 +18,7 @@
 from pandas.tseries import offsets, frequencies
 from pandas._libs import tslib, period
 from pandas._libs.tslibs.timezones import get_timezone
+from pandas._libs.tslibs.frequencies import _INVALID_FREQ_ERROR
 
 from pandas.compat import lrange, long, PY3
 from pandas.util.testing import assert_series_equal
@@ -744,8 +745,7 @@ def _check_round(freq, expected):
                                ('S', Timestamp('2000-01-05 05:09:15'))]:
             _check_round(freq, expected)
 
-        msg = frequencies._INVALID_FREQ_ERROR
-        with tm.assert_raises_regex(ValueError, msg):
+        with tm.assert_raises_regex(ValueError, _INVALID_FREQ_ERROR):
             stamp.round('foo')
 
     def test_class_ops_pytz(self):

From 0292fbe9c86469a8e2c923f9edfddea76a708e62 Mon Sep 17 00:00:00 2001
From: Brock Mendel <jbrockmendel@gmail.com>
Date: Fri, 10 Nov 2017 17:46:17 -0800
Subject: [PATCH 11/32] fix import

---
 pandas/tests/scalar/test_period_asfreq.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pandas/tests/scalar/test_period_asfreq.py b/pandas/tests/scalar/test_period_asfreq.py
index 295209930d435..a2819a3478f79 100644
--- a/pandas/tests/scalar/test_period_asfreq.py
+++ b/pandas/tests/scalar/test_period_asfreq.py
@@ -706,7 +706,7 @@ def test_asfreq_MS(self):
 
         assert initial.asfreq(freq="M", how="S") == Period('2013-01', 'M')
 
-        msg = pd._libs.tslibs._INVALID_FREQ_ERROR
+        msg = pd._libs.tslibs.frequencies._INVALID_FREQ_ERROR
         with tm.assert_raises_regex(ValueError, msg):
             initial.asfreq(freq="MS", how="S")
 

From 22f46ac30e23b5a9f6293efe9a3120bd2cb24020 Mon Sep 17 00:00:00 2001
From: Brock Mendel <jbrockmendel@gmail.com>
Date: Fri, 10 Nov 2017 20:10:39 -0800
Subject: [PATCH 12/32] remove unused import

---
 pandas/tests/scalar/test_timestamp.py | 1 -
 1 file changed, 1 deletion(-)

diff --git a/pandas/tests/scalar/test_timestamp.py b/pandas/tests/scalar/test_timestamp.py
index 08ef15936363e..fcb10d61915fd 100644
--- a/pandas/tests/scalar/test_timestamp.py
+++ b/pandas/tests/scalar/test_timestamp.py
@@ -15,7 +15,6 @@
 from pytz.exceptions import AmbiguousTimeError, NonExistentTimeError
 
 import pandas.util.testing as tm
-from pandas.tseries import offsets, frequencies
 from pandas._libs import tslib, period
 from pandas._libs.tslibs.timezones import get_timezone
 from pandas._libs.tslibs.frequencies import _INVALID_FREQ_ERROR

From bcc5ca1fec0e73e503f9d926486fd9d4c851b10a Mon Sep 17 00:00:00 2001
From: Brock Mendel <jbrockmendel@gmail.com>
Date: Sat, 11 Nov 2017 08:24:47 -0800
Subject: [PATCH 13/32] fixup missing import

---
 pandas/tests/scalar/test_timestamp.py | 1 +
 1 file changed, 1 insertion(+)

diff --git a/pandas/tests/scalar/test_timestamp.py b/pandas/tests/scalar/test_timestamp.py
index fcb10d61915fd..75572c8e08b88 100644
--- a/pandas/tests/scalar/test_timestamp.py
+++ b/pandas/tests/scalar/test_timestamp.py
@@ -26,6 +26,7 @@
                     Series, NaT, DataFrame, DatetimeIndex)
 from pandas.tseries.frequencies import (RESO_DAY, RESO_HR, RESO_MIN, RESO_US,
                                         RESO_MS, RESO_SEC)
+from pandas.tseries import offsets
 
 
 class TestTimestampArithmetic(object):

From 7bcdbe0ab242bd44d28bee4e98e32c77db5d27de Mon Sep 17 00:00:00 2001
From: Brock Mendel <jbrockmendel@gmail.com>
Date: Mon, 13 Nov 2017 12:29:22 -0800
Subject: [PATCH 14/32] fixup imports

---
 pandas/tests/indexes/period/test_tools.py | 5 +++--
 pandas/tests/test_resample.py             | 8 ++++----
 2 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/pandas/tests/indexes/period/test_tools.py b/pandas/tests/indexes/period/test_tools.py
index 0e65b4c300d47..cbad92a6fad3c 100644
--- a/pandas/tests/indexes/period/test_tools.py
+++ b/pandas/tests/indexes/period/test_tools.py
@@ -5,7 +5,8 @@
 import pandas.util.testing as tm
 import pandas.core.indexes.period as period
 from pandas.compat import lrange
-from pandas.tseries.frequencies import get_freq, MONTHS
+
+from pandas._libs.tslibs.frequencies import get_freq, _MONTHS
 from pandas._libs.period import period_ordinal, period_asfreq
 from pandas import (PeriodIndex, Period, DatetimeIndex, Timestamp, Series,
                     date_range, to_datetime, period_range)
@@ -335,7 +336,7 @@ def test_period_astype_to_timestamp(self):
 
     def test_to_period_quarterly(self):
         # make sure we can make the round trip
-        for month in MONTHS:
+        for month in _MONTHS:
             freq = 'Q-%s' % month
             rng = period_range('1989Q3', '1991Q3', freq=freq)
             stamps = rng.to_timestamp()
diff --git a/pandas/tests/test_resample.py b/pandas/tests/test_resample.py
index 61b2b689bffd6..58452cc70e67b 100644
--- a/pandas/tests/test_resample.py
+++ b/pandas/tests/test_resample.py
@@ -22,7 +22,7 @@
 from pandas.errors import UnsupportedFunctionCall
 from pandas.core.groupby import DataError
 from pandas._libs.tslibs.resolution import DAYS
-from pandas.tseries.frequencies import MONTHS
+from pandas._libs.tslibs.frequencies import _MONTHS
 from pandas.tseries.frequencies import to_offset
 from pandas.core.indexes.datetimes import date_range
 from pandas.tseries.offsets import Minute, BDay
@@ -2343,7 +2343,7 @@ def test_annual_upsample_M_e_b(self):
         self._check_annual_upsample_cases('M', 'end', 'bfill')
 
     def _check_annual_upsample_cases(self, targ, conv, meth, end='12/31/1991'):
-        for month in MONTHS:
+        for month in _MONTHS:
             ts = _simple_pts('1/1/1990', end, freq='A-%s' % month)
 
             result = getattr(ts.resample(targ, convention=conv), meth)()
@@ -2410,7 +2410,7 @@ def test_annual_upsample(self):
     def test_quarterly_upsample(self):
         targets = ['D', 'B', 'M']
 
-        for month in MONTHS:
+        for month in _MONTHS:
             ts = _simple_pts('1/1/1990', '12/31/1995', freq='Q-%s' % month)
 
             for targ, conv in product(targets, ['start', 'end']):
@@ -2547,7 +2547,7 @@ def test_resample_to_timestamps(self):
         assert_series_equal(result, expected)
 
     def test_resample_to_quarterly(self):
-        for month in MONTHS:
+        for month in _MONTHS:
             ts = _simple_pts('1990', '1992', freq='A-%s' % month)
             quar_ts = ts.resample('Q-%s' % month).ffill()
 

From 002930308ae72623334c4665bbde738087bc1528 Mon Sep 17 00:00:00 2001
From: Brock Mendel <jbrockmendel@gmail.com>
Date: Sun, 26 Nov 2017 10:00:00 -0800
Subject: [PATCH 15/32] Deprivatize, add typing per reviewer request

---
 pandas/_libs/period.pyx                      | 4 ++--
 pandas/_libs/tslibs/frequencies.pxd          | 6 +++---
 pandas/_libs/tslibs/frequencies.pyx          | 6 +++---
 pandas/tests/tseries/offsets/test_offsets.py | 4 ++--
 4 files changed, 10 insertions(+), 10 deletions(-)

diff --git a/pandas/_libs/period.pyx b/pandas/_libs/period.pyx
index 15e139ea65013..c9a6d2ba29576 100644
--- a/pandas/_libs/period.pyx
+++ b/pandas/_libs/period.pyx
@@ -32,7 +32,7 @@ from tslibs.timezones cimport (
 from tslibs.timedeltas cimport delta_to_nanoseconds
 
 from tslibs.frequencies cimport (get_freq_code, get_base_alias,
-                                 get_to_timestamp_base, _get_freq_str,
+                                 get_to_timestamp_base, get_freq_str,
                                  _get_rule_month)
 from tslibs.frequencies import _MONTH_NUMBERS
 from tslibs.parsing import parse_time_string, NAT_SENTINEL
@@ -573,7 +573,7 @@ cdef class _Period(object):
 
         if isinstance(freq, (int, tuple)):
             code, stride = get_freq_code(freq)
-            freq = _get_freq_str(code, stride)
+            freq = get_freq_str(code, stride)
 
         freq = frequencies.to_offset(freq)
 
diff --git a/pandas/_libs/tslibs/frequencies.pxd b/pandas/_libs/tslibs/frequencies.pxd
index b5bb3cd9dd596..e841a06c39e39 100644
--- a/pandas/_libs/tslibs/frequencies.pxd
+++ b/pandas/_libs/tslibs/frequencies.pxd
@@ -4,7 +4,7 @@
 cpdef object _get_rule_month(object source, object default=*)
 
 cpdef get_freq_code(freqstr)
-cpdef get_freq(freq)
+cpdef object get_freq(object freq)
 cpdef get_base_alias(freqstr)
-cpdef get_to_timestamp_base(base)
-cpdef _get_freq_str(base, mult=*)
+cpdef int get_to_timestamp_base(int base)
+cpdef str get_freq_str(base, mult=*)
diff --git a/pandas/_libs/tslibs/frequencies.pyx b/pandas/_libs/tslibs/frequencies.pyx
index 9debd72ad5510..779fdbb1829a4 100644
--- a/pandas/_libs/tslibs/frequencies.pyx
+++ b/pandas/_libs/tslibs/frequencies.pyx
@@ -210,7 +210,7 @@ cpdef _period_str_to_code(freqstr):
         raise ValueError(_INVALID_FREQ_ERROR.format(freqstr))
 
 
-cpdef _get_freq_str(base, mult=1):
+cpdef str get_freq_str(base, mult=1):
     code = _reverse_period_code_map.get(base)
     if mult == 1:
         return code
@@ -239,7 +239,7 @@ class FreqGroup(object):
     FR_NS = 12000
 
 
-cpdef get_to_timestamp_base(base):
+cpdef int get_to_timestamp_base(int base):
     """
     Return frequency code group used for base of to_timestamp against
     frequency code.
@@ -267,7 +267,7 @@ cpdef get_to_timestamp_base(base):
     return base
 
 
-cpdef get_freq(freq):
+cpdef object get_freq(object freq):
     """
     Return frequency code of given frequency str.
     If input is not string, return input as it is.
diff --git a/pandas/tests/tseries/offsets/test_offsets.py b/pandas/tests/tseries/offsets/test_offsets.py
index 5f92e7642b59e..85b8941238154 100644
--- a/pandas/tests/tseries/offsets/test_offsets.py
+++ b/pandas/tests/tseries/offsets/test_offsets.py
@@ -12,7 +12,7 @@
 
 from pandas.core.series import Series
 
-from pandas._libs.tslibs.frequencies import (get_freq_code, _get_freq_str,
+from pandas._libs.tslibs.frequencies import (get_freq_code, get_freq_str,
                                              _INVALID_FREQ_ERROR)
 from pandas.tseries.frequencies import (_offset_map,
                                         get_offset, get_standard_freq)
@@ -2895,7 +2895,7 @@ def test_rule_code(self):
             code, stride = get_freq_code('3' + k)
             assert isinstance(code, int)
             assert stride == 3
-            assert k == _get_freq_str(code)
+            assert k == get_freq_str(code)
 
 
 def test_dateoffset_misc():

From 957345babb3fc675da35b0955d90f5039d7dedab Mon Sep 17 00:00:00 2001
From: Brock Mendel <jbrockmendel@gmail.com>
Date: Sun, 26 Nov 2017 10:21:58 -0800
Subject: [PATCH 16/32] check set inclusion instead of list inclusion

---
 pandas/_libs/tslibs/frequencies.pyx | 52 ++++++++++++++---------------
 1 file changed, 26 insertions(+), 26 deletions(-)

diff --git a/pandas/_libs/tslibs/frequencies.pyx b/pandas/_libs/tslibs/frequencies.pyx
index 779fdbb1829a4..88595540810f6 100644
--- a/pandas/_libs/tslibs/frequencies.pyx
+++ b/pandas/_libs/tslibs/frequencies.pyx
@@ -315,31 +315,31 @@ def is_subperiod(source, target):
         if _is_quarterly(source):
             return _quarter_months_conform(_get_rule_month(source),
                                            _get_rule_month(target))
-        return source in ['D', 'C', 'B', 'M', 'H', 'T', 'S', 'L', 'U', 'N']
+        return source in {'D', 'C', 'B', 'M', 'H', 'T', 'S', 'L', 'U', 'N'}
     elif _is_quarterly(target):
-        return source in ['D', 'C', 'B', 'M', 'H', 'T', 'S', 'L', 'U', 'N']
+        return source in {'D', 'C', 'B', 'M', 'H', 'T', 'S', 'L', 'U', 'N'}
     elif _is_monthly(target):
-        return source in ['D', 'C', 'B', 'H', 'T', 'S', 'L', 'U', 'N']
+        return source in {'D', 'C', 'B', 'H', 'T', 'S', 'L', 'U', 'N'}
     elif _is_weekly(target):
-        return source in [target, 'D', 'C', 'B', 'H', 'T', 'S', 'L', 'U', 'N']
+        return source in {target, 'D', 'C', 'B', 'H', 'T', 'S', 'L', 'U', 'N'}
     elif target == 'B':
-        return source in ['B', 'H', 'T', 'S', 'L', 'U', 'N']
+        return source in {'B', 'H', 'T', 'S', 'L', 'U', 'N'}
     elif target == 'C':
-        return source in ['C', 'H', 'T', 'S', 'L', 'U', 'N']
+        return source in {'C', 'H', 'T', 'S', 'L', 'U', 'N'}
     elif target == 'D':
-        return source in ['D', 'H', 'T', 'S', 'L', 'U', 'N']
+        return source in {'D', 'H', 'T', 'S', 'L', 'U', 'N'}
     elif target == 'H':
-        return source in ['H', 'T', 'S', 'L', 'U', 'N']
+        return source in {'H', 'T', 'S', 'L', 'U', 'N'}
     elif target == 'T':
-        return source in ['T', 'S', 'L', 'U', 'N']
+        return source in {'T', 'S', 'L', 'U', 'N'}
     elif target == 'S':
-        return source in ['S', 'L', 'U', 'N']
+        return source in {'S', 'L', 'U', 'N'}
     elif target == 'L':
-        return source in ['L', 'U', 'N']
+        return source in {'L', 'U', 'N'}
     elif target == 'U':
-        return source in ['U', 'N']
+        return source in {'U', 'N'}
     elif target == 'N':
-        return source in ['N']
+        return source in {'N'}
 
 
 def is_superperiod(source, target):
@@ -371,31 +371,31 @@ def is_superperiod(source, target):
             smonth = _get_rule_month(source)
             tmonth = _get_rule_month(target)
             return _quarter_months_conform(smonth, tmonth)
-        return target in ['D', 'C', 'B', 'M', 'H', 'T', 'S', 'L', 'U', 'N']
+        return target in {'D', 'C', 'B', 'M', 'H', 'T', 'S', 'L', 'U', 'N'}
     elif _is_quarterly(source):
-        return target in ['D', 'C', 'B', 'M', 'H', 'T', 'S', 'L', 'U', 'N']
+        return target in {'D', 'C', 'B', 'M', 'H', 'T', 'S', 'L', 'U', 'N'}
     elif _is_monthly(source):
-        return target in ['D', 'C', 'B', 'H', 'T', 'S', 'L', 'U', 'N']
+        return target in {'D', 'C', 'B', 'H', 'T', 'S', 'L', 'U', 'N'}
     elif _is_weekly(source):
-        return target in [source, 'D', 'C', 'B', 'H', 'T', 'S', 'L', 'U', 'N']
+        return target in {source, 'D', 'C', 'B', 'H', 'T', 'S', 'L', 'U', 'N'}
     elif source == 'B':
-        return target in ['D', 'C', 'B', 'H', 'T', 'S', 'L', 'U', 'N']
+        return target in {'D', 'C', 'B', 'H', 'T', 'S', 'L', 'U', 'N'}
     elif source == 'C':
-        return target in ['D', 'C', 'B', 'H', 'T', 'S', 'L', 'U', 'N']
+        return target in {'D', 'C', 'B', 'H', 'T', 'S', 'L', 'U', 'N'}
     elif source == 'D':
-        return target in ['D', 'C', 'B', 'H', 'T', 'S', 'L', 'U', 'N']
+        return target in {'D', 'C', 'B', 'H', 'T', 'S', 'L', 'U', 'N'}
     elif source == 'H':
-        return target in ['H', 'T', 'S', 'L', 'U', 'N']
+        return target in {'H', 'T', 'S', 'L', 'U', 'N'}
     elif source == 'T':
-        return target in ['T', 'S', 'L', 'U', 'N']
+        return target in {'T', 'S', 'L', 'U', 'N'}
     elif source == 'S':
-        return target in ['S', 'L', 'U', 'N']
+        return target in {'S', 'L', 'U', 'N'}
     elif source == 'L':
-        return target in ['L', 'U', 'N']
+        return target in {'L', 'U', 'N'}
     elif source == 'U':
-        return target in ['U', 'N']
+        return target in {'U', 'N'}
     elif source == 'N':
-        return target in ['N']
+        return target in {'N'}
 
 
 def _maybe_coerce_freq(code):

From 4c200b29154ec635b3befde6dbc8fdd168035d4c Mon Sep 17 00:00:00 2001
From: Brock Mendel <jbrockmendel@gmail.com>
Date: Wed, 29 Nov 2017 10:06:32 -0800
Subject: [PATCH 17/32] fix broken import

---
 pandas/tests/tseries/offsets/test_fiscal.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/pandas/tests/tseries/offsets/test_fiscal.py b/pandas/tests/tseries/offsets/test_fiscal.py
index 45f12c6931fd9..a3d16e8561c46 100644
--- a/pandas/tests/tseries/offsets/test_fiscal.py
+++ b/pandas/tests/tseries/offsets/test_fiscal.py
@@ -9,7 +9,8 @@
 
 import pandas.util.testing as tm
 
-from pandas.tseries.frequencies import get_offset, _INVALID_FREQ_ERROR
+from pandas.tseries.frequencies import get_offset
+from pandas._libs.tslibs.frequencies import _INVALID_FREQ_ERROR
 from pandas.tseries.offsets import FY5253Quarter, FY5253
 from pandas._libs.tslibs.offsets import WeekDay
 

From aa0f988f06ae58b6ae803d0334eee739f3eea63e Mon Sep 17 00:00:00 2001
From: Brock Mendel <jbrockmendel@gmail.com>
Date: Wed, 29 Nov 2017 18:52:22 -0800
Subject: [PATCH 18/32] dummy commit to force CI

---
 pandas/_libs/tslibs/parsing.pyx | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/pandas/_libs/tslibs/parsing.pyx b/pandas/_libs/tslibs/parsing.pyx
index 90882eefd9f67..8ce1d9cdf2158 100644
--- a/pandas/_libs/tslibs/parsing.pyx
+++ b/pandas/_libs/tslibs/parsing.pyx
@@ -1,8 +1,5 @@
 # -*- coding: utf-8 -*-
 # cython: profile=False
-# cython: linetrace=False
-# distutils: define_macros=CYTHON_TRACE=0
-# distutils: define_macros=CYTHON_TRACE_NOGIL=0
 """
 Parsing functions for datetime and datetime-like strings.
 """

From 2138285bbadecf13e1328e2b00b0b4f3d556445e Mon Sep 17 00:00:00 2001
From: Brock Mendel <jbrockmendel@gmail.com>
Date: Sun, 10 Dec 2017 18:10:09 -0800
Subject: [PATCH 19/32] centralize+deprivatize day/month constants in ccalendar

---
 pandas/_libs/tslibs/ccalendar.pyx         | 11 ++++++++
 pandas/_libs/tslibs/frequencies.pyx       | 10 +++----
 pandas/_libs/tslibs/offsets.pyx           | 25 +++--------------
 pandas/_libs/tslibs/parsing.pyx           |  8 +++---
 pandas/_libs/tslibs/period.pyx            |  4 +--
 pandas/_libs/tslibs/resolution.pyx        | 18 +++++--------
 pandas/tests/indexes/period/test_tools.py |  5 ++--
 pandas/tests/scalar/test_period.py        |  2 +-
 pandas/tests/test_resample.py             | 10 +++----
 pandas/tseries/offsets.py                 | 33 ++++++++++++-----------
 10 files changed, 56 insertions(+), 70 deletions(-)

diff --git a/pandas/_libs/tslibs/ccalendar.pyx b/pandas/_libs/tslibs/ccalendar.pyx
index a68ecbd2e8629..f45fe11c73c04 100644
--- a/pandas/_libs/tslibs/ccalendar.pyx
+++ b/pandas/_libs/tslibs/ccalendar.pyx
@@ -33,6 +33,17 @@ cdef int32_t* _month_offset = [
     0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365,
     0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335, 366]
 
+# Canonical location for other modules to find name constants
+MONTHS = ['JAN', 'FEB', 'MAR', 'APR', 'MAY', 'JUN', 'JUL',
+          'AUG', 'SEP', 'OCT', 'NOV', 'DEC']
+MONTH_NUMBERS = {name: num for num, name in enumerate(MONTHS)}
+MONTH_ALIASES = {(num + 1): name for num, name in enumerate(MONTHS)}
+MONTH_TO_CAL_NUM = {name: num + 1 for num, name in enumerate(MONTHS)}
+
+DAYS = ['MON', 'TUE', 'WED', 'THU', 'FRI', 'SAT', 'SUN']
+int_to_weekday = {num: name for num, name in enumerate(DAYS)}
+weekday_to_int = {_int_to_weekday[key]: key for key in _int_to_weekday}
+
 # ----------------------------------------------------------------------
 
 
diff --git a/pandas/_libs/tslibs/frequencies.pyx b/pandas/_libs/tslibs/frequencies.pyx
index 88595540810f6..bad6335d693f2 100644
--- a/pandas/_libs/tslibs/frequencies.pyx
+++ b/pandas/_libs/tslibs/frequencies.pyx
@@ -11,13 +11,11 @@ np.import_array()
 
 from util cimport is_integer_object, is_string_object
 
+from ccalendar import MONTH_NUMBERS
+
 # ----------------------------------------------------------------------
 # Constants
 
-_MONTHS = ['JAN', 'FEB', 'MAR', 'APR', 'MAY', 'JUN', 'JUL',
-           'AUG', 'SEP', 'OCT', 'NOV', 'DEC']
-_MONTH_NUMBERS = {k: i for i, k in enumerate(_MONTHS)}
-
 # hack to handle WOM-1MON
 opattern = re.compile(
     r'([+\-]?\d*|[+\-]?\d*\.\d*)\s*([A-Za-z]+([\-][\dA-Za-z\-]+)?)'
@@ -419,8 +417,8 @@ def _maybe_coerce_freq(code):
 
 
 def _quarter_months_conform(source, target):
-    snum = _MONTH_NUMBERS[source]
-    tnum = _MONTH_NUMBERS[target]
+    snum = MONTH_NUMBERS[source]
+    tnum = MONTH_NUMBERS[target]
     return snum % 3 == tnum % 3
 
 
diff --git a/pandas/_libs/tslibs/offsets.pyx b/pandas/_libs/tslibs/offsets.pyx
index 29e14103dfe20..e6266d520541a 100644
--- a/pandas/_libs/tslibs/offsets.pyx
+++ b/pandas/_libs/tslibs/offsets.pyx
@@ -17,6 +17,7 @@ np.import_array()
 
 from util cimport is_string_object, is_integer_object
 
+from ccalendar import MONTHS, MONTH_ALIASES
 from conversion cimport tz_convert_single, pydt_to_i8
 from frequencies cimport get_freq_code
 from nattype cimport NPY_NAT
@@ -27,13 +28,7 @@ from np_datetime cimport (pandas_datetimestruct,
 # ---------------------------------------------------------------------
 # Constants
 
-# Duplicated in tslib
-_MONTHS = ['JAN', 'FEB', 'MAR', 'APR', 'MAY', 'JUN', 'JUL',
-           'AUG', 'SEP', 'OCT', 'NOV', 'DEC']
-_int_to_month = {(k + 1): v for k, v in enumerate(_MONTHS)}
-_month_to_int = {v: k for k, v in _int_to_month.items()}
-
-
+# TODO: remove this; it is only used in tests
 class WeekDay(object):
     MON = 0
     TUE = 1
@@ -44,18 +39,6 @@ class WeekDay(object):
     SUN = 6
 
 
-_int_to_weekday = {
-    WeekDay.MON: 'MON',
-    WeekDay.TUE: 'TUE',
-    WeekDay.WED: 'WED',
-    WeekDay.THU: 'THU',
-    WeekDay.FRI: 'FRI',
-    WeekDay.SAT: 'SAT',
-    WeekDay.SUN: 'SUN'}
-
-_weekday_to_int = {_int_to_weekday[key]: key for key in _int_to_weekday}
-
-
 _offset_to_period_map = {
     'WEEKDAY': 'D',
     'EOM': 'M',
@@ -88,12 +71,12 @@ _offset_to_period_map = {
 need_suffix = ['QS', 'BQ', 'BQS', 'YS', 'AS', 'BY', 'BA', 'BYS', 'BAS']
 
 for __prefix in need_suffix:
-    for _m in _MONTHS:
+    for _m in MONTHS:
         key = '%s-%s' % (__prefix, _m)
         _offset_to_period_map[key] = _offset_to_period_map[__prefix]
 
 for __prefix in ['A', 'Q']:
-    for _m in _MONTHS:
+    for _m in MONTHS:
         _alias = '%s-%s' % (__prefix, _m)
         _offset_to_period_map[_alias] = _alias
 
diff --git a/pandas/_libs/tslibs/parsing.pyx b/pandas/_libs/tslibs/parsing.pyx
index 8ce1d9cdf2158..1bfaa7b804a99 100644
--- a/pandas/_libs/tslibs/parsing.pyx
+++ b/pandas/_libs/tslibs/parsing.pyx
@@ -41,6 +41,8 @@ from dateutil.relativedelta import relativedelta
 from dateutil.parser import DEFAULTPARSER
 from dateutil.parser import parse as du_parse
 
+from ccalendar import MONTH_NUMBERS
+
 # ----------------------------------------------------------------------
 # Constants
 
@@ -53,10 +55,6 @@ _nat_strings = set(['NaT', 'nat', 'NAT', 'nan', 'NaN', 'NAN'])
 
 _DEFAULT_DATETIME = datetime(1, 1, 1).replace(hour=0, minute=0,
                                               second=0, microsecond=0)
-_MONTHS = ['JAN', 'FEB', 'MAR', 'APR', 'MAY', 'JUN', 'JUL',
-           'AUG', 'SEP', 'OCT', 'NOV', 'DEC']
-_MONTH_NUMBERS = {k: i for i, k in enumerate(_MONTHS)}
-_MONTH_ALIASES = {(k + 1): v for k, v in enumerate(_MONTHS)}
 
 cdef object _TIMEPAT = re.compile(r'^([01]?[0-9]|2[0-3]):([0-5][0-9])')
 
@@ -267,7 +265,7 @@ cdef inline object _parse_dateabbr_string(object date_string, object default,
             if freq is not None:
                 # hack attack, #1228
                 try:
-                    mnum = _MONTH_NUMBERS[_get_rule_month(freq)] + 1
+                    mnum = MONTH_NUMBERS[_get_rule_month(freq)] + 1
                 except (KeyError, ValueError):
                     msg = ('Unable to retrieve month information from given '
                            'freq: {0}').format(freq)
diff --git a/pandas/_libs/tslibs/period.pyx b/pandas/_libs/tslibs/period.pyx
index f87c0f35e72cc..8a08012283d63 100644
--- a/pandas/_libs/tslibs/period.pyx
+++ b/pandas/_libs/tslibs/period.pyx
@@ -33,10 +33,10 @@ from timestamps import Timestamp
 from timezones cimport is_utc, is_tzlocal, get_utcoffset, get_dst_info
 from timedeltas cimport delta_to_nanoseconds
 
+from ccalendar import MONTH_NUMBERS
 from frequencies cimport (get_freq_code, get_base_alias,
                           get_to_timestamp_base, get_freq_str,
                           _get_rule_month)
-from frequencies import _MONTH_NUMBERS
 from parsing import parse_time_string, NAT_SENTINEL
 from resolution import resolution, Resolution
 from nattype import nat_strings, NaT, iNaT
@@ -1151,7 +1151,7 @@ def _quarter_to_myear(year, quarter, freq):
         if quarter <= 0 or quarter > 4:
             raise ValueError('Quarter must be 1 <= q <= 4')
 
-        mnum = _MONTH_NUMBERS[_get_rule_month(freq)] + 1
+        mnum = MONTH_NUMBERS[_get_rule_month(freq)] + 1
         month = (mnum + (quarter - 1) * 3) % 12 + 1
         if month > mnum:
             year -= 1
diff --git a/pandas/_libs/tslibs/resolution.pyx b/pandas/_libs/tslibs/resolution.pyx
index d2b518c74a1e3..87175af17e495 100644
--- a/pandas/_libs/tslibs/resolution.pyx
+++ b/pandas/_libs/tslibs/resolution.pyx
@@ -24,6 +24,7 @@ from timezones cimport (is_utc, is_tzlocal,
                         maybe_get_tz, get_dst_info, get_utcoffset)
 from fields import build_field_sarray
 from conversion import tz_convert
+from ccalendar import MONTHS, DAYS, MONTH_ALIASES, int_to_weekday
 
 from pandas._libs.properties import cache_readonly
 from pandas._libs.tslib import Timestamp
@@ -50,13 +51,6 @@ _ONE_MINUTE = 60 * _ONE_SECOND
 _ONE_HOUR = 60 * _ONE_MINUTE
 _ONE_DAY = 24 * _ONE_HOUR
 
-DAYS = ['MON', 'TUE', 'WED', 'THU', 'FRI', 'SAT', 'SUN']
-_weekday_rule_aliases = {k: v for k, v in enumerate(DAYS)}
-
-_MONTHS = ['JAN', 'FEB', 'MAR', 'APR', 'MAY', 'JUN', 'JUL',
-           'AUG', 'SEP', 'OCT', 'NOV', 'DEC']
-_MONTH_ALIASES = {(k + 1): v for k, v in enumerate(_MONTHS)}
-
 # ----------------------------------------------------------------------
 
 cpdef resolution(ndarray[int64_t] stamps, tz=None):
@@ -537,7 +531,7 @@ class _FrequencyInferer(object):
         annual_rule = self._get_annual_rule()
         if annual_rule:
             nyears = self.ydiffs[0]
-            month = _MONTH_ALIASES[self.rep_stamp.month]
+            month = MONTH_ALIASES[self.rep_stamp.month]
             alias = '{prefix}-{month}'.format(prefix=annual_rule, month=month)
             return _maybe_add_count(alias, nyears)
 
@@ -545,7 +539,7 @@ class _FrequencyInferer(object):
         if quarterly_rule:
             nquarters = self.mdiffs[0] / 3
             mod_dict = {0: 12, 2: 11, 1: 10}
-            month = _MONTH_ALIASES[mod_dict[self.rep_stamp.month % 3]]
+            month = MONTH_ALIASES[mod_dict[self.rep_stamp.month % 3]]
             alias = '{prefix}-{month}'.format(prefix=quarterly_rule,
                                               month=month)
             return _maybe_add_count(alias, nquarters)
@@ -558,7 +552,7 @@ class _FrequencyInferer(object):
             days = self.deltas[0] / _ONE_DAY
             if days % 7 == 0:
                 # Weekly
-                day = _weekday_rule_aliases[self.rep_stamp.weekday()]
+                day = int_to_weekday[self.rep_stamp.weekday()]
                 return _maybe_add_count('W-{day}'.format(day=day), days / 7)
             else:
                 return _maybe_add_count('D', days)
@@ -630,7 +624,7 @@ class _FrequencyInferer(object):
 
         # get which week
         week = week_of_months[0] + 1
-        wd = _weekday_rule_aliases[weekdays[0]]
+        wd = int_to_weekday[weekdays[0]]
 
         return 'WOM-{week}{weekday}'.format(week=week, weekday=wd)
 
@@ -642,7 +636,7 @@ class _TimedeltaFrequencyInferer(_FrequencyInferer):
             days = self.deltas[0] / _ONE_DAY
             if days % 7 == 0:
                 # Weekly
-                wd = _weekday_rule_aliases[self.rep_stamp.weekday()]
+                wd = int_to_weekday[self.rep_stamp.weekday()]
                 alias = 'W-{weekday}'.format(weekday=wd)
                 return _maybe_add_count(alias, days / 7)
             else:
diff --git a/pandas/tests/indexes/period/test_tools.py b/pandas/tests/indexes/period/test_tools.py
index 007178a9413da..2523441a21285 100644
--- a/pandas/tests/indexes/period/test_tools.py
+++ b/pandas/tests/indexes/period/test_tools.py
@@ -6,8 +6,9 @@
 import pandas.core.indexes.period as period
 from pandas.compat import lrange
 
-from pandas._libs.tslibs.frequencies import get_freq, _MONTHS
+from pandas._libs.tslibs.frequencies import get_freq
 from pandas._libs.tslibs.period import period_ordinal, period_asfreq
+from pandas._libs.ccalendar import MONTHS
 
 from pandas import (PeriodIndex, Period, DatetimeIndex, Timestamp, Series,
                     date_range, to_datetime, period_range)
@@ -337,7 +338,7 @@ def test_period_astype_to_timestamp(self):
 
     def test_to_period_quarterly(self):
         # make sure we can make the round trip
-        for month in _MONTHS:
+        for month in MONTHS:
             freq = 'Q-%s' % month
             rng = period_range('1989Q3', '1991Q3', freq=freq)
             stamps = rng.to_timestamp()
diff --git a/pandas/tests/scalar/test_period.py b/pandas/tests/scalar/test_period.py
index 0a54f5e70c87e..706e1a4a76b22 100644
--- a/pandas/tests/scalar/test_period.py
+++ b/pandas/tests/scalar/test_period.py
@@ -14,7 +14,7 @@
 from pandas._libs.tslibs import period as libperiod
 from pandas._libs.tslibs.parsing import DateParseError
 from pandas import Period, Timestamp, offsets
-from pandas._libs.tslibs.resolution import DAYS, _MONTHS as MONTHS
+from pandas._libs.tslibs.ccalendar import DAYS, MONTHS
 
 
 class TestPeriodProperties(object):
diff --git a/pandas/tests/test_resample.py b/pandas/tests/test_resample.py
index f2d06a7fe2628..669e71eb0fead 100644
--- a/pandas/tests/test_resample.py
+++ b/pandas/tests/test_resample.py
@@ -22,8 +22,8 @@
 from pandas.core.base import SpecificationError, AbstractMethodError
 from pandas.errors import UnsupportedFunctionCall
 from pandas.core.groupby import DataError
-from pandas._libs.tslibs.resolution import DAYS
-from pandas._libs.tslibs.frequencies import _MONTHS
+
+from pandas._libs.tslibs.ccalendar import DAYS, MONTHS
 from pandas.tseries.frequencies import to_offset
 from pandas.core.indexes.datetimes import date_range
 from pandas.tseries.offsets import Minute, BDay
@@ -2334,7 +2334,7 @@ def test_annual_upsample_M_e_b(self):
         self._check_annual_upsample_cases('M', 'end', 'bfill')
 
     def _check_annual_upsample_cases(self, targ, conv, meth, end='12/31/1991'):
-        for month in _MONTHS:
+        for month in MONTHS:
             ts = _simple_pts('1/1/1990', end, freq='A-%s' % month)
 
             result = getattr(ts.resample(targ, convention=conv), meth)()
@@ -2401,7 +2401,7 @@ def test_annual_upsample(self):
     def test_quarterly_upsample(self):
         targets = ['D', 'B', 'M']
 
-        for month in _MONTHS:
+        for month in MONTHS:
             ts = _simple_pts('1/1/1990', '12/31/1995', freq='Q-%s' % month)
 
             for targ, conv in product(targets, ['start', 'end']):
@@ -2538,7 +2538,7 @@ def test_resample_to_timestamps(self):
         assert_series_equal(result, expected)
 
     def test_resample_to_quarterly(self):
-        for month in _MONTHS:
+        for month in MONTHS:
             ts = _simple_pts('1990', '1992', freq='A-%s' % month)
             quar_ts = ts.resample('Q-%s' % month).ffill()
 
diff --git a/pandas/tseries/offsets.py b/pandas/tseries/offsets.py
index dd5f01a36a43e..8b12b2f3ad2ce 100644
--- a/pandas/tseries/offsets.py
+++ b/pandas/tseries/offsets.py
@@ -16,13 +16,13 @@
 from pandas._libs import tslib, Timestamp, OutOfBoundsDatetime, Timedelta
 from pandas.util._decorators import cache_readonly
 
+from pandas._libs.tslibs import ccalendar
 from pandas._libs.tslibs.timedeltas import delta_to_nanoseconds
 import pandas._libs.tslibs.offsets as liboffsets
 from pandas._libs.tslibs.offsets import (
     ApplyTypeError,
     as_datetime, _is_normalized,
     _get_calendar, _to_dt64, _validate_business_time,
-    _int_to_weekday, _weekday_to_int,
     _determine_offset,
     apply_index_wraps,
     roll_yearday,
@@ -933,7 +933,7 @@ def name(self):
         if self.isAnchored:
             return self.rule_code
         else:
-            month = liboffsets._int_to_month[self.n]
+            month = ccalendar.MONTH_ALIASES[self.n]
             return "{code}-{month}".format(code=self.rule_code,
                                            month=month)
 
@@ -1348,7 +1348,8 @@ def onOffset(self, dt):
     def rule_code(self):
         suffix = ''
         if self.weekday is not None:
-            suffix = '-{weekday}'.format(weekday=_int_to_weekday[self.weekday])
+            weekday = ccalendar.int_to_weekday[self.weekday]
+            suffix = '-{weekday}'.format(weekday=weekday)
         return self._prefix + suffix
 
     @classmethod
@@ -1356,7 +1357,7 @@ def _from_name(cls, suffix=None):
         if not suffix:
             weekday = None
         else:
-            weekday = _weekday_to_int[suffix]
+            weekday = ccalendar.weekday_to_int[suffix]
         return cls(weekday=weekday)
 
 
@@ -1430,7 +1431,7 @@ def onOffset(self, dt):
 
     @property
     def rule_code(self):
-        weekday = _int_to_weekday.get(self.weekday, '')
+        weekday = ccalendar.int_to_weekday.get(self.weekday, '')
         return '{prefix}-{week}{weekday}'.format(prefix=self._prefix,
                                                  week=self.week + 1,
                                                  weekday=weekday)
@@ -1443,7 +1444,7 @@ def _from_name(cls, suffix=None):
         # TODO: handle n here...
         # only one digit weeks (1 --> week 0, 2 --> week 1, etc.)
         week = int(suffix[0]) - 1
-        weekday = _weekday_to_int[suffix[1:]]
+        weekday = ccalendar.weekday_to_int[suffix[1:]]
         return cls(week=week, weekday=weekday)
 
 
@@ -1509,7 +1510,7 @@ def onOffset(self, dt):
 
     @property
     def rule_code(self):
-        weekday = _int_to_weekday.get(self.weekday, '')
+        weekday = ccalendar.int_to_weekday.get(self.weekday, '')
         return '{prefix}-{weekday}'.format(prefix=self._prefix,
                                            weekday=weekday)
 
@@ -1519,7 +1520,7 @@ def _from_name(cls, suffix=None):
             raise ValueError("Prefix {prefix!r} requires a suffix."
                              .format(prefix=cls._prefix))
         # TODO: handle n here...
-        weekday = _weekday_to_int[suffix]
+        weekday = ccalendar.weekday_to_int[suffix]
         return cls(weekday=weekday)
 
 # ---------------------------------------------------------------------
@@ -1550,7 +1551,7 @@ def isAnchored(self):
     def _from_name(cls, suffix=None):
         kwargs = {}
         if suffix:
-            kwargs['startingMonth'] = liboffsets._month_to_int[suffix]
+            kwargs['startingMonth'] = ccalendar.MONTH_TO_CAL_NUM[suffix]
         else:
             if cls._from_name_startingMonth is not None:
                 kwargs['startingMonth'] = cls._from_name_startingMonth
@@ -1558,7 +1559,7 @@ def _from_name(cls, suffix=None):
 
     @property
     def rule_code(self):
-        month = liboffsets._int_to_month[self.startingMonth]
+        month = ccalendar.MONTH_ALIASES[self.startingMonth]
         return '{prefix}-{month}'.format(prefix=self._prefix, month=month)
 
     @apply_wraps
@@ -1681,12 +1682,12 @@ def __init__(self, n=1, normalize=False, month=None):
     def _from_name(cls, suffix=None):
         kwargs = {}
         if suffix:
-            kwargs['month'] = liboffsets._month_to_int[suffix]
+            kwargs['month'] = ccalendar.MONTH_TO_CAL_NUM[suffix]
         return cls(**kwargs)
 
     @property
     def rule_code(self):
-        month = liboffsets._int_to_month[self.month]
+        month = ccalendar.MONTH_ALIASES[self.month]
         return '{prefix}-{month}'.format(prefix=self._prefix, month=month)
 
 
@@ -1906,8 +1907,8 @@ def _get_suffix_prefix(self):
 
     def get_rule_code_suffix(self):
         prefix = self._get_suffix_prefix()
-        month = liboffsets._int_to_month[self.startingMonth]
-        weekday = _int_to_weekday[self.weekday]
+        month = ccalendar.MONTH_ALIASES[self.startingMonth]
+        weekday = ccalendar.int_to_weekday[self.weekday]
         return '{prefix}-{month}-{weekday}'.format(prefix=prefix, month=month,
                                                    weekday=weekday)
 
@@ -1921,8 +1922,8 @@ def _parse_suffix(cls, varion_code, startingMonth_code, weekday_code):
             raise ValueError("Unable to parse varion_code: "
                              "{code}".format(code=varion_code))
 
-        startingMonth = liboffsets._month_to_int[startingMonth_code]
-        weekday = _weekday_to_int[weekday_code]
+        startingMonth = ccalendar.MONTH_TO_CAL_NUM[startingMonth_code]
+        weekday = ccalendar.weekday_to_int[weekday_code]
 
         return {"weekday": weekday,
                 "startingMonth": startingMonth,

From cb73bd6bb0a72545499bf0169577d6369c80e622 Mon Sep 17 00:00:00 2001
From: Brock Mendel <jbrockmendel@gmail.com>
Date: Sun, 10 Dec 2017 19:12:40 -0800
Subject: [PATCH 20/32] fixup typo

---
 pandas/_libs/tslibs/ccalendar.pyx | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pandas/_libs/tslibs/ccalendar.pyx b/pandas/_libs/tslibs/ccalendar.pyx
index f45fe11c73c04..d7edae865911a 100644
--- a/pandas/_libs/tslibs/ccalendar.pyx
+++ b/pandas/_libs/tslibs/ccalendar.pyx
@@ -42,7 +42,7 @@ MONTH_TO_CAL_NUM = {name: num + 1 for num, name in enumerate(MONTHS)}
 
 DAYS = ['MON', 'TUE', 'WED', 'THU', 'FRI', 'SAT', 'SUN']
 int_to_weekday = {num: name for num, name in enumerate(DAYS)}
-weekday_to_int = {_int_to_weekday[key]: key for key in _int_to_weekday}
+weekday_to_int = {int_to_weekday[key]: key for key in int_to_weekday}
 
 # ----------------------------------------------------------------------
 

From db3717bd63d3264e3b0b6568b37a24db0e188ee7 Mon Sep 17 00:00:00 2001
From: Brock Mendel <jbrockmendel@gmail.com>
Date: Sun, 10 Dec 2017 22:00:15 -0800
Subject: [PATCH 21/32] add typing

---
 pandas/_libs/tslibs/frequencies.pyx | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/pandas/_libs/tslibs/frequencies.pyx b/pandas/_libs/tslibs/frequencies.pyx
index bad6335d693f2..d46f187d9f843 100644
--- a/pandas/_libs/tslibs/frequencies.pyx
+++ b/pandas/_libs/tslibs/frequencies.pyx
@@ -416,28 +416,28 @@ def _maybe_coerce_freq(code):
     return code.upper()
 
 
-def _quarter_months_conform(source, target):
+cdef bint _quarter_months_conform(str source, str target):
     snum = MONTH_NUMBERS[source]
     tnum = MONTH_NUMBERS[target]
     return snum % 3 == tnum % 3
 
 
-def _is_annual(rule):
+cdef bint _is_annual(str rule):
     rule = rule.upper()
     return rule == 'A' or rule.startswith('A-')
 
 
-def _is_quarterly(rule):
+cdef bint _is_quarterly(str rule):
     rule = rule.upper()
     return rule == 'Q' or rule.startswith('Q-') or rule.startswith('BQ')
 
 
-def _is_monthly(rule):
+cdef bint _is_monthly(str rule):
     rule = rule.upper()
     return rule == 'M' or rule == 'BM'
 
 
-def _is_weekly(rule):
+cdef bint _is_weekly(str rule):
     rule = rule.upper()
     return rule == 'W' or rule.startswith('W-')
 

From cbefe3e3948c3edc633e398db549d6ab85fcafc5 Mon Sep 17 00:00:00 2001
From: Brock Mendel <jbrockmendel@gmail.com>
Date: Sun, 10 Dec 2017 22:02:09 -0800
Subject: [PATCH 22/32] remove unused imports

---
 pandas/_libs/tslibs/resolution.pyx | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pandas/_libs/tslibs/resolution.pyx b/pandas/_libs/tslibs/resolution.pyx
index 87175af17e495..c7c53b0afdf4a 100644
--- a/pandas/_libs/tslibs/resolution.pyx
+++ b/pandas/_libs/tslibs/resolution.pyx
@@ -24,7 +24,7 @@ from timezones cimport (is_utc, is_tzlocal,
                         maybe_get_tz, get_dst_info, get_utcoffset)
 from fields import build_field_sarray
 from conversion import tz_convert
-from ccalendar import MONTHS, DAYS, MONTH_ALIASES, int_to_weekday
+from ccalendar import MONTH_ALIASES, int_to_weekday
 
 from pandas._libs.properties import cache_readonly
 from pandas._libs.tslib import Timestamp

From d1c67bca7e9dc9110459dcce99c517081327a466 Mon Sep 17 00:00:00 2001
From: Brock Mendel <jbrockmendel@gmail.com>
Date: Mon, 11 Dec 2017 08:26:27 -0800
Subject: [PATCH 23/32] fixup typo broken import

---
 pandas/tests/indexes/period/test_tools.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pandas/tests/indexes/period/test_tools.py b/pandas/tests/indexes/period/test_tools.py
index 2523441a21285..0e72cadb5d494 100644
--- a/pandas/tests/indexes/period/test_tools.py
+++ b/pandas/tests/indexes/period/test_tools.py
@@ -8,7 +8,7 @@
 
 from pandas._libs.tslibs.frequencies import get_freq
 from pandas._libs.tslibs.period import period_ordinal, period_asfreq
-from pandas._libs.ccalendar import MONTHS
+from pandas._libs.tslibs.ccalendar import MONTHS
 
 from pandas import (PeriodIndex, Period, DatetimeIndex, Timestamp, Series,
                     date_range, to_datetime, period_range)

From f60fe4df99f50287ee046ed38e1349d34c31baca Mon Sep 17 00:00:00 2001
From: Brock Mendel <jbrockmendel@gmail.com>
Date: Mon, 11 Dec 2017 08:26:51 -0800
Subject: [PATCH 24/32] de-privatize get_rule_month

---
 pandas/_libs/tslibs/frequencies.pxd      |  2 +-
 pandas/_libs/tslibs/frequencies.pyx      | 16 ++++++-------
 pandas/_libs/tslibs/period.pyx           |  4 ++--
 pandas/tests/tseries/test_frequencies.py | 30 ++++++++++++------------
 4 files changed, 26 insertions(+), 26 deletions(-)

diff --git a/pandas/_libs/tslibs/frequencies.pxd b/pandas/_libs/tslibs/frequencies.pxd
index e841a06c39e39..4c0ade74285fc 100644
--- a/pandas/_libs/tslibs/frequencies.pxd
+++ b/pandas/_libs/tslibs/frequencies.pxd
@@ -1,7 +1,7 @@
 # -*- coding: utf-8 -*-
 # cython: profile=False
 
-cpdef object _get_rule_month(object source, object default=*)
+cpdef object get_rule_month(object source, object default=*)
 
 cpdef get_freq_code(freqstr)
 cpdef object get_freq(object freq)
diff --git a/pandas/_libs/tslibs/frequencies.pyx b/pandas/_libs/tslibs/frequencies.pyx
index d46f187d9f843..deb15d182d005 100644
--- a/pandas/_libs/tslibs/frequencies.pyx
+++ b/pandas/_libs/tslibs/frequencies.pyx
@@ -311,8 +311,8 @@ def is_subperiod(source, target):
 
     if _is_annual(target):
         if _is_quarterly(source):
-            return _quarter_months_conform(_get_rule_month(source),
-                                           _get_rule_month(target))
+            return _quarter_months_conform(get_rule_month(source),
+                                           get_rule_month(target))
         return source in {'D', 'C', 'B', 'M', 'H', 'T', 'S', 'L', 'U', 'N'}
     elif _is_quarterly(target):
         return source in {'D', 'C', 'B', 'M', 'H', 'T', 'S', 'L', 'U', 'N'}
@@ -363,11 +363,11 @@ def is_superperiod(source, target):
 
     if _is_annual(source):
         if _is_annual(target):
-            return _get_rule_month(source) == _get_rule_month(target)
+            return get_rule_month(source) == get_rule_month(target)
 
         if _is_quarterly(target):
-            smonth = _get_rule_month(source)
-            tmonth = _get_rule_month(target)
+            smonth = get_rule_month(source)
+            tmonth = get_rule_month(target)
             return _quarter_months_conform(smonth, tmonth)
         return target in {'D', 'C', 'B', 'M', 'H', 'T', 'S', 'L', 'U', 'N'}
     elif _is_quarterly(source):
@@ -444,16 +444,16 @@ cdef bint _is_weekly(str rule):
 
 # ----------------------------------------------------------------------
 
-cpdef object _get_rule_month(object source, object default='DEC'):
+cpdef object get_rule_month(object source, object default='DEC'):
     """
     Return starting month of given freq, default is December.
 
     Example
     -------
-    >>> _get_rule_month('D')
+    >>> get_rule_month('D')
     'DEC'
 
-    >>> _get_rule_month('A-JAN')
+    >>> get_rule_month('A-JAN')
     'JAN'
     """
     if hasattr(source, 'freqstr'):
diff --git a/pandas/_libs/tslibs/period.pyx b/pandas/_libs/tslibs/period.pyx
index 8a08012283d63..46365035a0b9a 100644
--- a/pandas/_libs/tslibs/period.pyx
+++ b/pandas/_libs/tslibs/period.pyx
@@ -36,7 +36,7 @@ from timedeltas cimport delta_to_nanoseconds
 from ccalendar import MONTH_NUMBERS
 from frequencies cimport (get_freq_code, get_base_alias,
                           get_to_timestamp_base, get_freq_str,
-                          _get_rule_month)
+                          get_rule_month)
 from parsing import parse_time_string, NAT_SENTINEL
 from resolution import resolution, Resolution
 from nattype import nat_strings, NaT, iNaT
@@ -1151,7 +1151,7 @@ def _quarter_to_myear(year, quarter, freq):
         if quarter <= 0 or quarter > 4:
             raise ValueError('Quarter must be 1 <= q <= 4')
 
-        mnum = MONTH_NUMBERS[_get_rule_month(freq)] + 1
+        mnum = MONTH_NUMBERS[get_rule_month(freq)] + 1
         month = (mnum + (quarter - 1) * 3) % 12 + 1
         if month > mnum:
             year -= 1
diff --git a/pandas/tests/tseries/test_frequencies.py b/pandas/tests/tseries/test_frequencies.py
index 7afec1c11b74d..7bdc1b4b0f164 100644
--- a/pandas/tests/tseries/test_frequencies.py
+++ b/pandas/tests/tseries/test_frequencies.py
@@ -7,7 +7,7 @@
 from pandas import (Index, DatetimeIndex, Timestamp, Series,
                     date_range, period_range)
 
-from pandas._libs.tslibs.frequencies import (_period_code_map, _get_rule_month,
+from pandas._libs.tslibs.frequencies import (_period_code_map, get_rule_month,
                                              _period_str_to_code,
                                              _INVALID_FREQ_ERROR)
 
@@ -289,38 +289,38 @@ def test_rule_aliases():
 
 
 def test_get_rule_month():
-    result = _get_rule_month('W')
+    result = get_rule_month('W')
     assert (result == 'DEC')
-    result = _get_rule_month(offsets.Week())
+    result = get_rule_month(offsets.Week())
     assert (result == 'DEC')
 
-    result = _get_rule_month('D')
+    result = get_rule_month('D')
     assert (result == 'DEC')
-    result = _get_rule_month(offsets.Day())
+    result = get_rule_month(offsets.Day())
     assert (result == 'DEC')
 
-    result = _get_rule_month('Q')
+    result = get_rule_month('Q')
     assert (result == 'DEC')
-    result = _get_rule_month(offsets.QuarterEnd(startingMonth=12))
+    result = get_rule_month(offsets.QuarterEnd(startingMonth=12))
     print(result == 'DEC')
 
-    result = _get_rule_month('Q-JAN')
+    result = get_rule_month('Q-JAN')
     assert (result == 'JAN')
-    result = _get_rule_month(offsets.QuarterEnd(startingMonth=1))
+    result = get_rule_month(offsets.QuarterEnd(startingMonth=1))
     assert (result == 'JAN')
 
-    result = _get_rule_month('A-DEC')
+    result = get_rule_month('A-DEC')
     assert (result == 'DEC')
-    result = _get_rule_month('Y-DEC')
+    result = get_rule_month('Y-DEC')
     assert (result == 'DEC')
-    result = _get_rule_month(offsets.YearEnd())
+    result = get_rule_month(offsets.YearEnd())
     assert (result == 'DEC')
 
-    result = _get_rule_month('A-MAY')
+    result = get_rule_month('A-MAY')
     assert (result == 'MAY')
-    result = _get_rule_month('Y-MAY')
+    result = get_rule_month('Y-MAY')
     assert (result == 'MAY')
-    result = _get_rule_month(offsets.YearEnd(month=5))
+    result = get_rule_month(offsets.YearEnd(month=5))
     assert (result == 'MAY')
 
 

From f250550ee6a8fa4ce99ad6be0f33c58b4185d619 Mon Sep 17 00:00:00 2001
From: Brock Mendel <jbrockmendel@gmail.com>
Date: Mon, 11 Dec 2017 15:07:18 -0800
Subject: [PATCH 25/32] remove unused import

---
 pandas/_libs/tslibs/offsets.pyx | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pandas/_libs/tslibs/offsets.pyx b/pandas/_libs/tslibs/offsets.pyx
index e6266d520541a..0c88bc4e42adf 100644
--- a/pandas/_libs/tslibs/offsets.pyx
+++ b/pandas/_libs/tslibs/offsets.pyx
@@ -17,7 +17,7 @@ np.import_array()
 
 from util cimport is_string_object, is_integer_object
 
-from ccalendar import MONTHS, MONTH_ALIASES
+from ccalendar import MONTHS
 from conversion cimport tz_convert_single, pydt_to_i8
 from frequencies cimport get_freq_code
 from nattype cimport NPY_NAT

From 23a3588a5a703dab180942b7e3c30bfd649d320d Mon Sep 17 00:00:00 2001
From: Brock Mendel <jbrockmendel@gmail.com>
Date: Wed, 20 Dec 2017 11:21:11 -0800
Subject: [PATCH 26/32] add types and docstrings

---
 pandas/_libs/tslibs/frequencies.pxd |  2 +-
 pandas/_libs/tslibs/frequencies.pyx | 79 +++++++++++++++++++++--------
 2 files changed, 60 insertions(+), 21 deletions(-)

diff --git a/pandas/_libs/tslibs/frequencies.pxd b/pandas/_libs/tslibs/frequencies.pxd
index 4c0ade74285fc..98d600c540ace 100644
--- a/pandas/_libs/tslibs/frequencies.pxd
+++ b/pandas/_libs/tslibs/frequencies.pxd
@@ -5,6 +5,6 @@ cpdef object get_rule_month(object source, object default=*)
 
 cpdef get_freq_code(freqstr)
 cpdef object get_freq(object freq)
-cpdef get_base_alias(freqstr)
+cpdef str get_base_alias(freqstr)
 cpdef int get_to_timestamp_base(int base)
 cpdef str get_freq_str(base, mult=*)
diff --git a/pandas/_libs/tslibs/frequencies.pyx b/pandas/_libs/tslibs/frequencies.pyx
index deb15d182d005..f8030ca20d975 100644
--- a/pandas/_libs/tslibs/frequencies.pyx
+++ b/pandas/_libs/tslibs/frequencies.pyx
@@ -26,6 +26,21 @@ _INVALID_FREQ_ERROR = "Invalid frequency: {0}"
 # ---------------------------------------------------------------------
 # Period codes
 
+class FreqGroup(object):
+    FR_ANN = 1000
+    FR_QTR = 2000
+    FR_MTH = 3000
+    FR_WK = 4000
+    FR_BUS = 5000
+    FR_DAY = 6000
+    FR_HR = 7000
+    FR_MIN = 8000
+    FR_SEC = 9000
+    FR_MS = 10000
+    FR_US = 11000
+    FR_NS = 12000
+
+
 # period frequency constants corresponding to scikits timeseries
 # originals
 _period_code_map = {
@@ -209,39 +224,54 @@ cpdef _period_str_to_code(freqstr):
 
 
 cpdef str get_freq_str(base, mult=1):
+    """
+    Return the summary string associated with this offset code, possibly
+    adjusted by a multiplier.
+
+    Parameters
+    ----------
+    base : int (member of FreqGroup)
+
+    Returns
+    -------
+    freq_str : str
+
+    Examples
+    --------
+    >>> get_freq_str(1000)
+    'A-DEC'
+
+    >>> get_freq_str(2000, 2)
+    '2Q-DEC'
+
+    >>> get_freq_str("foo")
+    """
     code = _reverse_period_code_map.get(base)
     if mult == 1:
         return code
     return str(mult) + code
 
 
-cpdef get_base_alias(freqstr):
+cpdef str get_base_alias(freqstr):
     """
     Returns the base frequency alias, e.g., '5D' -> 'D'
     """
     return _base_and_stride(freqstr)[0]
 
 
-class FreqGroup(object):
-    FR_ANN = 1000
-    FR_QTR = 2000
-    FR_MTH = 3000
-    FR_WK = 4000
-    FR_BUS = 5000
-    FR_DAY = 6000
-    FR_HR = 7000
-    FR_MIN = 8000
-    FR_SEC = 9000
-    FR_MS = 10000
-    FR_US = 11000
-    FR_NS = 12000
-
-
 cpdef int get_to_timestamp_base(int base):
     """
     Return frequency code group used for base of to_timestamp against
     frequency code.
 
+    Parameters
+    ----------
+    base : int (member of FreqGroup)
+
+    Returns
+    -------
+    base : int
+
     Example
     -------
     # Return day freq code against longer freq than day
@@ -287,7 +317,7 @@ cpdef object get_freq(object freq):
 # ----------------------------------------------------------------------
 # Frequency comparison
 
-def is_subperiod(source, target):
+cpdef bool is_subperiod(source, target):
     """
     Returns True if downsampling is possible between source and target
     frequencies
@@ -340,7 +370,7 @@ def is_subperiod(source, target):
         return source in {'N'}
 
 
-def is_superperiod(source, target):
+cpdef bool is_superperiod(source, target):
     """
     Returns True if upsampling is possible between source and target
     frequencies
@@ -396,7 +426,7 @@ def is_superperiod(source, target):
         return target in {'N'}
 
 
-def _maybe_coerce_freq(code):
+cdef str _maybe_coerce_freq(str code):
     """ we might need to coerce a code to a rule_code
     and uppercase it
 
@@ -407,7 +437,7 @@ def _maybe_coerce_freq(code):
 
     Returns
     -------
-    string code
+    code : string
     """
     assert code is not None
     if getattr(code, '_typ', None) == 'dateoffset':
@@ -448,6 +478,15 @@ cpdef object get_rule_month(object source, object default='DEC'):
     """
     Return starting month of given freq, default is December.
 
+    Parameters
+    ----------
+    source : object
+    default : object (default "DEC")
+
+    Returns
+    -------
+    rule_month: object (usually string)
+
     Example
     -------
     >>> get_rule_month('D')

From a7f063cf474eb5ec3e846ef9c3d0637dc2cf8c73 Mon Sep 17 00:00:00 2001
From: Brock Mendel <jbrockmendel@gmail.com>
Date: Wed, 20 Dec 2017 11:40:54 -0800
Subject: [PATCH 27/32] typo fixup bool-->bint

---
 pandas/_libs/tslibs/frequencies.pyx | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/pandas/_libs/tslibs/frequencies.pyx b/pandas/_libs/tslibs/frequencies.pyx
index f8030ca20d975..f7258abaf09c9 100644
--- a/pandas/_libs/tslibs/frequencies.pyx
+++ b/pandas/_libs/tslibs/frequencies.pyx
@@ -317,7 +317,7 @@ cpdef object get_freq(object freq):
 # ----------------------------------------------------------------------
 # Frequency comparison
 
-cpdef bool is_subperiod(source, target):
+cpdef bint is_subperiod(source, target):
     """
     Returns True if downsampling is possible between source and target
     frequencies
@@ -370,7 +370,7 @@ cpdef bool is_subperiod(source, target):
         return source in {'N'}
 
 
-cpdef bool is_superperiod(source, target):
+cpdef bint is_superperiod(source, target):
     """
     Returns True if upsampling is possible between source and target
     frequencies

From 3ee6e921bd5907363da1abea9ea97c026418ec2c Mon Sep 17 00:00:00 2001
From: Brock Mendel <jbrockmendel@gmail.com>
Date: Wed, 20 Dec 2017 17:26:54 -0800
Subject: [PATCH 28/32] fix typing

---
 pandas/_libs/tslibs/frequencies.pyx | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/pandas/_libs/tslibs/frequencies.pyx b/pandas/_libs/tslibs/frequencies.pyx
index f7258abaf09c9..2bdfcacfbb8b4 100644
--- a/pandas/_libs/tslibs/frequencies.pyx
+++ b/pandas/_libs/tslibs/frequencies.pyx
@@ -324,9 +324,9 @@ cpdef bint is_subperiod(source, target):
 
     Parameters
     ----------
-    source : string
+    source : string or DateOffset
         Frequency converting from
-    target : string
+    target : string or DateOffset
         Frequency converting to
 
     Returns
@@ -426,13 +426,13 @@ cpdef bint is_superperiod(source, target):
         return target in {'N'}
 
 
-cdef str _maybe_coerce_freq(str code):
+cdef str _maybe_coerce_freq(code):
     """ we might need to coerce a code to a rule_code
     and uppercase it
 
     Parameters
     ----------
-    source : string
+    source : string or DateOffset
         Frequency converting from
 
     Returns

From 64ef864bf750f57d7a3e73983e4ce64d21e8419c Mon Sep 17 00:00:00 2001
From: Brock Mendel <jbrockmendel@gmail.com>
Date: Wed, 20 Dec 2017 19:32:42 -0800
Subject: [PATCH 29/32] whitespace fixup

---
 pandas/_libs/tslibs/frequencies.pyx | 1 +
 1 file changed, 1 insertion(+)

diff --git a/pandas/_libs/tslibs/frequencies.pyx b/pandas/_libs/tslibs/frequencies.pyx
index 2bdfcacfbb8b4..097403997c1ce 100644
--- a/pandas/_libs/tslibs/frequencies.pyx
+++ b/pandas/_libs/tslibs/frequencies.pyx
@@ -26,6 +26,7 @@ _INVALID_FREQ_ERROR = "Invalid frequency: {0}"
 # ---------------------------------------------------------------------
 # Period codes
 
+
 class FreqGroup(object):
     FR_ANN = 1000
     FR_QTR = 2000

From 6d62e04e4c995508beac791ee320a6d0e1c21fc8 Mon Sep 17 00:00:00 2001
From: Brock Mendel <jbrockmendel@gmail.com>
Date: Sat, 23 Dec 2017 18:19:08 -0800
Subject: [PATCH 30/32] implement test_libfrequencies per request

---
 pandas/tests/tseries/test_frequencies.py    | 116 +-------------------
 pandas/tests/tseries/test_libfrequencies.py | 116 ++++++++++++++++++++
 2 files changed, 118 insertions(+), 114 deletions(-)
 create mode 100644 pandas/tests/tseries/test_libfrequencies.py

diff --git a/pandas/tests/tseries/test_frequencies.py b/pandas/tests/tseries/test_frequencies.py
index 7bdc1b4b0f164..d4a232cf9ae0b 100644
--- a/pandas/tests/tseries/test_frequencies.py
+++ b/pandas/tests/tseries/test_frequencies.py
@@ -7,10 +7,9 @@
 from pandas import (Index, DatetimeIndex, Timestamp, Series,
                     date_range, period_range)
 
-from pandas._libs.tslibs.frequencies import (_period_code_map, get_rule_month,
-                                             _period_str_to_code,
+from pandas._libs.tslibs.frequencies import (_period_code_map,
                                              _INVALID_FREQ_ERROR)
-
+from pandas._libs.tslibs.ccalendar import MONTHS
 from pandas._libs.tslibs import resolution
 import pandas.tseries.frequencies as frequencies
 from pandas.core.tools.datetimes import to_datetime
@@ -288,87 +287,6 @@ def test_rule_aliases():
     assert rule == offsets.Micro(10)
 
 
-def test_get_rule_month():
-    result = get_rule_month('W')
-    assert (result == 'DEC')
-    result = get_rule_month(offsets.Week())
-    assert (result == 'DEC')
-
-    result = get_rule_month('D')
-    assert (result == 'DEC')
-    result = get_rule_month(offsets.Day())
-    assert (result == 'DEC')
-
-    result = get_rule_month('Q')
-    assert (result == 'DEC')
-    result = get_rule_month(offsets.QuarterEnd(startingMonth=12))
-    print(result == 'DEC')
-
-    result = get_rule_month('Q-JAN')
-    assert (result == 'JAN')
-    result = get_rule_month(offsets.QuarterEnd(startingMonth=1))
-    assert (result == 'JAN')
-
-    result = get_rule_month('A-DEC')
-    assert (result == 'DEC')
-    result = get_rule_month('Y-DEC')
-    assert (result == 'DEC')
-    result = get_rule_month(offsets.YearEnd())
-    assert (result == 'DEC')
-
-    result = get_rule_month('A-MAY')
-    assert (result == 'MAY')
-    result = get_rule_month('Y-MAY')
-    assert (result == 'MAY')
-    result = get_rule_month(offsets.YearEnd(month=5))
-    assert (result == 'MAY')
-
-
-def test_period_str_to_code():
-    assert (_period_str_to_code('A') == 1000)
-    assert (_period_str_to_code('A-DEC') == 1000)
-    assert (_period_str_to_code('A-JAN') == 1001)
-    assert (_period_str_to_code('Y') == 1000)
-    assert (_period_str_to_code('Y-DEC') == 1000)
-    assert (_period_str_to_code('Y-JAN') == 1001)
-
-    assert (_period_str_to_code('Q') == 2000)
-    assert (_period_str_to_code('Q-DEC') == 2000)
-    assert (_period_str_to_code('Q-FEB') == 2002)
-
-    def _assert_depr(freq, expected, aliases):
-        assert isinstance(aliases, list)
-        assert (_period_str_to_code(freq) == expected)
-
-        msg = _INVALID_FREQ_ERROR
-        for alias in aliases:
-            with tm.assert_raises_regex(ValueError, msg):
-                _period_str_to_code(alias)
-
-    _assert_depr("M", 3000, ["MTH", "MONTH", "MONTHLY"])
-
-    assert (_period_str_to_code('W') == 4000)
-    assert (_period_str_to_code('W-SUN') == 4000)
-    assert (_period_str_to_code('W-FRI') == 4005)
-
-    _assert_depr("B", 5000, ["BUS", "BUSINESS", "BUSINESSLY", "WEEKDAY"])
-    _assert_depr("D", 6000, ["DAY", "DLY", "DAILY"])
-    _assert_depr("H", 7000, ["HR", "HOUR", "HRLY", "HOURLY"])
-
-    _assert_depr("T", 8000, ["minute", "MINUTE", "MINUTELY"])
-    assert (_period_str_to_code('Min') == 8000)
-
-    _assert_depr("S", 9000, ["sec", "SEC", "SECOND", "SECONDLY"])
-    _assert_depr("L", 10000, ["MILLISECOND", "MILLISECONDLY"])
-    assert (_period_str_to_code('ms') == 10000)
-
-    _assert_depr("U", 11000, ["MICROSECOND", "MICROSECONDLY"])
-    assert (_period_str_to_code('US') == 11000)
-
-    _assert_depr("N", 12000, ["NANOSECOND", "NANOSECONDLY"])
-    assert (_period_str_to_code('NS') == 12000)
-
-
 class TestFrequencyCode(object):
 
     def test_freq_code(self):
@@ -890,33 +808,3 @@ def test_legacy_offset_warnings(self):
 
             with tm.assert_raises_regex(ValueError, msg):
                 date_range('2011-01-01', periods=5, freq=freq)
-
-
-MONTHS = ['JAN', 'FEB', 'MAR', 'APR', 'MAY', 'JUN', 'JUL', 'AUG', 'SEP', 'OCT',
-          'NOV', 'DEC']
-
-
-def test_is_superperiod_subperiod():
-
-    # input validation
-    assert not (frequencies.is_superperiod(offsets.YearEnd(), None))
-    assert not (frequencies.is_subperiod(offsets.MonthEnd(), None))
-    assert not (frequencies.is_superperiod(None, offsets.YearEnd()))
-    assert not (frequencies.is_subperiod(None, offsets.MonthEnd()))
-    assert not (frequencies.is_superperiod(None, None))
-    assert not (frequencies.is_subperiod(None, None))
-
-    assert (frequencies.is_superperiod(offsets.YearEnd(), offsets.MonthEnd()))
-    assert (frequencies.is_subperiod(offsets.MonthEnd(), offsets.YearEnd()))
-
-    assert (frequencies.is_superperiod(offsets.Hour(), offsets.Minute()))
-    assert (frequencies.is_subperiod(offsets.Minute(), offsets.Hour()))
-
-    assert (frequencies.is_superperiod(offsets.Second(), offsets.Milli()))
-    assert (frequencies.is_subperiod(offsets.Milli(), offsets.Second()))
-
-    assert (frequencies.is_superperiod(offsets.Milli(), offsets.Micro()))
-    assert (frequencies.is_subperiod(offsets.Micro(), offsets.Milli()))
-
-    assert (frequencies.is_superperiod(offsets.Micro(), offsets.Nano()))
-    assert (frequencies.is_subperiod(offsets.Nano(), offsets.Micro()))
diff --git a/pandas/tests/tseries/test_libfrequencies.py b/pandas/tests/tseries/test_libfrequencies.py
new file mode 100644
index 0000000000000..bac4e8db40f2b
--- /dev/null
+++ b/pandas/tests/tseries/test_libfrequencies.py
@@ -0,0 +1,116 @@
+# -*- coding: utf-8 -*-
+
+import pandas.util.testing as tm
+
+from pandas.tseries import offsets
+from pandas._libs.tslibs.frequencies import (get_rule_month,
+                                             _period_str_to_code,
+                                             _INVALID_FREQ_ERROR,
+                                             is_superperiod, is_subperiod)
+
+
+def test_get_rule_month():
+    result = get_rule_month('W')
+    assert (result == 'DEC')
+    result = get_rule_month(offsets.Week())
+    assert (result == 'DEC')
+
+    result = get_rule_month('D')
+    assert (result == 'DEC')
+    result = get_rule_month(offsets.Day())
+    assert (result == 'DEC')
+
+    result = get_rule_month('Q')
+    assert (result == 'DEC')
+    result = get_rule_month(offsets.QuarterEnd(startingMonth=12))
+    print(result == 'DEC')
+
+    result = get_rule_month('Q-JAN')
+    assert (result == 'JAN')
+    result = get_rule_month(offsets.QuarterEnd(startingMonth=1))
+    assert (result == 'JAN')
+
+    result = get_rule_month('A-DEC')
+    assert (result == 'DEC')
+    result = get_rule_month('Y-DEC')
+    assert (result == 'DEC')
+    result = get_rule_month(offsets.YearEnd())
+    assert (result == 'DEC')
+
+    result = get_rule_month('A-MAY')
+    assert (result == 'MAY')
+    result = get_rule_month('Y-MAY')
+    assert (result == 'MAY')
+    result = get_rule_month(offsets.YearEnd(month=5))
+    assert (result == 'MAY')
+
+
+def test_period_str_to_code():
+    assert (_period_str_to_code('A') == 1000)
+    assert (_period_str_to_code('A-DEC') == 1000)
+    assert (_period_str_to_code('A-JAN') == 1001)
+    assert (_period_str_to_code('Y') == 1000)
+    assert (_period_str_to_code('Y-DEC') == 1000)
+    assert (_period_str_to_code('Y-JAN') == 1001)
+
+    assert (_period_str_to_code('Q') == 2000)
+    assert (_period_str_to_code('Q-DEC') == 2000)
+    assert (_period_str_to_code('Q-FEB') == 2002)
+
+    def _assert_depr(freq, expected, aliases):
+        assert isinstance(aliases, list)
+        assert (_period_str_to_code(freq) == expected)
+
+        msg = _INVALID_FREQ_ERROR
+        for alias in aliases:
+            with tm.assert_raises_regex(ValueError, msg):
+                _period_str_to_code(alias)
+
+    _assert_depr("M", 3000, ["MTH", "MONTH", "MONTHLY"])
+
+    assert (_period_str_to_code('W') == 4000)
+    assert (_period_str_to_code('W-SUN') == 4000)
+    assert (_period_str_to_code('W-FRI') == 4005)
+
+    _assert_depr("B", 5000, ["BUS", "BUSINESS", "BUSINESSLY", "WEEKDAY"])
+    _assert_depr("D", 6000, ["DAY", "DLY", "DAILY"])
+    _assert_depr("H", 7000, ["HR", "HOUR", "HRLY", "HOURLY"])
+
+    _assert_depr("T", 8000, ["minute", "MINUTE", "MINUTELY"])
+    assert (_period_str_to_code('Min') == 8000)
+
+    _assert_depr("S", 9000, ["sec", "SEC", "SECOND", "SECONDLY"])
+    _assert_depr("L", 10000, ["MILLISECOND", "MILLISECONDLY"])
+    assert (_period_str_to_code('ms') == 10000)
+
+    _assert_depr("U", 11000, ["MICROSECOND", "MICROSECONDLY"])
+    assert (_period_str_to_code('US') == 11000)
+
+    _assert_depr("N", 12000, ["NANOSECOND", "NANOSECONDLY"])
+    assert (_period_str_to_code('NS') == 12000)
+
+
+def test_is_superperiod_subperiod():
+
+    # input validation
+    assert not (is_superperiod(offsets.YearEnd(), None))
+    assert not (is_subperiod(offsets.MonthEnd(), None))
+    assert not (is_superperiod(None, offsets.YearEnd()))
+    assert not (is_subperiod(None, offsets.MonthEnd()))
+    assert not (is_superperiod(None, None))
+    assert not (is_subperiod(None, None))
+
+    assert (is_superperiod(offsets.YearEnd(), offsets.MonthEnd()))
+    assert (is_subperiod(offsets.MonthEnd(), offsets.YearEnd()))
+
+    assert (is_superperiod(offsets.Hour(), offsets.Minute()))
+    assert (is_subperiod(offsets.Minute(), offsets.Hour()))
+
+    assert (is_superperiod(offsets.Second(), offsets.Milli()))
+    assert (is_subperiod(offsets.Milli(), offsets.Second()))
+
+    assert (is_superperiod(offsets.Milli(), offsets.Micro()))
+    assert (is_subperiod(offsets.Micro(), offsets.Milli()))
+
+    assert (is_superperiod(offsets.Micro(), offsets.Nano()))
+    assert (is_subperiod(offsets.Nano(), offsets.Micro()))

From 1d71924615daad7361dd36b0886434ebd2a25387 Mon Sep 17 00:00:00 2001
From: Brock Mendel <jbrockmendel@gmail.com>
Date: Sat, 23 Dec 2017 18:21:55 -0800
Subject: [PATCH 31/32] extend docstring per request

---
 pandas/_libs/tslibs/frequencies.pyx | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/pandas/_libs/tslibs/frequencies.pyx b/pandas/_libs/tslibs/frequencies.pyx
index 097403997c1ce..78f6594363707 100644
--- a/pandas/_libs/tslibs/frequencies.pyx
+++ b/pandas/_libs/tslibs/frequencies.pyx
@@ -256,6 +256,14 @@ cpdef str get_freq_str(base, mult=1):
 cpdef str get_base_alias(freqstr):
     """
     Returns the base frequency alias, e.g., '5D' -> 'D'
+
+    Parameters
+    ----------
+    freqstr : str
+
+    Returns
+    -------
+    base_alias : str
     """
     return _base_and_stride(freqstr)[0]
 
@@ -291,7 +299,7 @@ cpdef int get_to_timestamp_base(int base):
     """
     if base < FreqGroup.FR_BUS:
         return FreqGroup.FR_DAY
-    if FreqGroup.FR_HR <= base <= FreqGroup.FR_SEC:
+    elif FreqGroup.FR_HR <= base <= FreqGroup.FR_SEC:
         return FreqGroup.FR_SEC
     return base
 

From 8129b1c4efe278610571805cf77ea41325c028d6 Mon Sep 17 00:00:00 2001
From: Brock Mendel <jbrockmendel@gmail.com>
Date: Thu, 4 Jan 2018 10:22:56 -0800
Subject: [PATCH 32/32] fix docstrings, rename _assert_depr

---
 pandas/_libs/tslibs/frequencies.pyx         | 16 ++++-----
 pandas/tests/tseries/test_libfrequencies.py | 38 ++++++++++-----------
 2 files changed, 27 insertions(+), 27 deletions(-)

diff --git a/pandas/_libs/tslibs/frequencies.pyx b/pandas/_libs/tslibs/frequencies.pyx
index 78f6594363707..cce3600371300 100644
--- a/pandas/_libs/tslibs/frequencies.pyx
+++ b/pandas/_libs/tslibs/frequencies.pyx
@@ -144,8 +144,8 @@ cpdef get_freq_code(freqstr):
     -------
     return : tuple of base frequency code and stride (mult)
 
-    Example
-    -------
+    Examples
+    --------
     >>> get_freq_code('3D')
     (6000, 3)
 
@@ -281,8 +281,8 @@ cpdef int get_to_timestamp_base(int base):
     -------
     base : int
 
-    Example
-    -------
+    Examples
+    --------
     # Return day freq code against longer freq than day
     >>> get_to_timestamp_base(get_freq_code('D')[0])
     6000
@@ -309,8 +309,8 @@ cpdef object get_freq(object freq):
     Return frequency code of given frequency str.
     If input is not string, return input as it is.
 
-    Example
-    -------
+    Examples
+    --------
     >>> get_freq('A')
     1000
 
@@ -496,8 +496,8 @@ cpdef object get_rule_month(object source, object default='DEC'):
     -------
     rule_month: object (usually string)
 
-    Example
-    -------
+    Examples
+    --------
     >>> get_rule_month('D')
     'DEC'
 
diff --git a/pandas/tests/tseries/test_libfrequencies.py b/pandas/tests/tseries/test_libfrequencies.py
index bac4e8db40f2b..601d542da3095 100644
--- a/pandas/tests/tseries/test_libfrequencies.py
+++ b/pandas/tests/tseries/test_libfrequencies.py
@@ -9,6 +9,15 @@
                                              is_superperiod, is_subperiod)
 
 
+def assert_aliases_deprecated(freq, expected, aliases):
+    assert isinstance(aliases, list)
+    assert (_period_str_to_code(freq) == expected)
+
+    for alias in aliases:
+        with tm.assert_raises_regex(ValueError, _INVALID_FREQ_ERROR):
+            _period_str_to_code(alias)
+
+
 def test_get_rule_month():
     result = get_rule_month('W')
     assert (result == 'DEC')
@@ -23,7 +32,6 @@ def test_get_rule_month():
     result = get_rule_month('Q')
     assert (result == 'DEC')
     result = get_rule_month(offsets.QuarterEnd(startingMonth=12))
-    print(result == 'DEC')
 
     result = get_rule_month('Q-JAN')
     assert (result == 'JAN')
@@ -57,36 +65,28 @@ def test_period_str_to_code():
     assert (_period_str_to_code('Q-DEC') == 2000)
     assert (_period_str_to_code('Q-FEB') == 2002)
 
-    def _assert_depr(freq, expected, aliases):
-        assert isinstance(aliases, list)
-        assert (_period_str_to_code(freq) == expected)
-
-        msg = _INVALID_FREQ_ERROR
-        for alias in aliases:
-            with tm.assert_raises_regex(ValueError, msg):
-                _period_str_to_code(alias)
-
-    _assert_depr("M", 3000, ["MTH", "MONTH", "MONTHLY"])
+    assert_aliases_deprecated("M", 3000, ["MTH", "MONTH", "MONTHLY"])
 
     assert (_period_str_to_code('W') == 4000)
     assert (_period_str_to_code('W-SUN') == 4000)
     assert (_period_str_to_code('W-FRI') == 4005)
 
-    _assert_depr("B", 5000, ["BUS", "BUSINESS", "BUSINESSLY", "WEEKDAY"])
-    _assert_depr("D", 6000, ["DAY", "DLY", "DAILY"])
-    _assert_depr("H", 7000, ["HR", "HOUR", "HRLY", "HOURLY"])
+    assert_aliases_deprecated("B", 5000, ["BUS", "BUSINESS",
+                                          "BUSINESSLY", "WEEKDAY"])
+    assert_aliases_deprecated("D", 6000, ["DAY", "DLY", "DAILY"])
+    assert_aliases_deprecated("H", 7000, ["HR", "HOUR", "HRLY", "HOURLY"])
 
-    _assert_depr("T", 8000, ["minute", "MINUTE", "MINUTELY"])
+    assert_aliases_deprecated("T", 8000, ["minute", "MINUTE", "MINUTELY"])
     assert (_period_str_to_code('Min') == 8000)
 
-    _assert_depr("S", 9000, ["sec", "SEC", "SECOND", "SECONDLY"])
-    _assert_depr("L", 10000, ["MILLISECOND", "MILLISECONDLY"])
+    assert_aliases_deprecated("S", 9000, ["sec", "SEC", "SECOND", "SECONDLY"])
+    assert_aliases_deprecated("L", 10000, ["MILLISECOND", "MILLISECONDLY"])
     assert (_period_str_to_code('ms') == 10000)
 
-    _assert_depr("U", 11000, ["MICROSECOND", "MICROSECONDLY"])
+    assert_aliases_deprecated("U", 11000, ["MICROSECOND", "MICROSECONDLY"])
     assert (_period_str_to_code('US') == 11000)
 
-    _assert_depr("N", 12000, ["NANOSECOND", "NANOSECONDLY"])
+    assert_aliases_deprecated("N", 12000, ["NANOSECOND", "NANOSECONDLY"])
     assert (_period_str_to_code('NS') == 12000)