From c0cbbbefc729e9295c008b206df6dd58c81e8733 Mon Sep 17 00:00:00 2001
From: Brock Mendel <jbrockmendel@gmail.com>
Date: Mon, 15 Oct 2018 16:38:38 -0700
Subject: [PATCH 01/11] small fixups

---
 pandas/core/arrays/datetimelike.py | 4 ++--
 pandas/core/indexes/period.py      | 6 +++---
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/pandas/core/arrays/datetimelike.py b/pandas/core/arrays/datetimelike.py
index a98b0b3bf35f9..62b9f685c009a 100644
--- a/pandas/core/arrays/datetimelike.py
+++ b/pandas/core/arrays/datetimelike.py
@@ -380,7 +380,7 @@ def _add_delta_tdi(self, other):
         Add a delta of a TimedeltaIndex
         return the i8 result view
         """
-        if not len(self) == len(other):
+        if len(self) != len(other):
             raise ValueError("cannot add indices of unequal length")
 
         if isinstance(other, np.ndarray):
@@ -441,7 +441,7 @@ def _sub_period_array(self, other):
                             .format(dtype=other.dtype,
                                     cls=type(self).__name__))
 
-        if not len(self) == len(other):
+        if len(self) != len(other):
             raise ValueError("cannot subtract arrays/indices of "
                              "unequal length")
         if self.freq != other.freq:
diff --git a/pandas/core/indexes/period.py b/pandas/core/indexes/period.py
index f452a57e82725..64a70b52b02a6 100644
--- a/pandas/core/indexes/period.py
+++ b/pandas/core/indexes/period.py
@@ -289,9 +289,9 @@ def __array_wrap__(self, result, context=None):
         """
         if isinstance(context, tuple) and len(context) > 0:
             func = context[0]
-            if (func is np.add):
+            if func is np.add:
                 pass
-            elif (func is np.subtract):
+            elif func is np.subtract:
                 name = self.name
                 left = context[1][0]
                 right = context[1][1]
@@ -312,7 +312,7 @@ def __array_wrap__(self, result, context=None):
             return result
         # the result is object dtype array of Period
         # cannot pass _simple_new as it is
-        return self._shallow_copy(result, freq=self.freq, name=self.name)
+        return type(self)(result, freq=self.freq, name=self.name)
 
     @property
     def size(self):

From 8622871ea32d065654cebc950f9314f98dca7cd4 Mon Sep 17 00:00:00 2001
From: Brock Mendel <jbrockmendel@gmail.com>
Date: Mon, 15 Oct 2018 16:39:37 -0700
Subject: [PATCH 02/11] import abstractmethoderror at top

---
 pandas/core/arrays/datetimelike.py | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/pandas/core/arrays/datetimelike.py b/pandas/core/arrays/datetimelike.py
index 62b9f685c009a..7fbda6b4c1a1f 100644
--- a/pandas/core/arrays/datetimelike.py
+++ b/pandas/core/arrays/datetimelike.py
@@ -11,7 +11,8 @@
 from pandas._libs.tslibs.period import (
     Period, DIFFERENT_FREQ_INDEX, IncompatibleFrequency)
 
-from pandas.errors import NullFrequencyError, PerformanceWarning
+from pandas.errors import (
+    NullFrequencyError, PerformanceWarning, AbstractMethodError)
 from pandas import compat
 
 from pandas.tseries import frequencies
@@ -77,12 +78,10 @@ class AttributesMixin(object):
     @property
     def _attributes(self):
         # Inheriting subclass should implement _attributes as a list of strings
-        from pandas.errors import AbstractMethodError
         raise AbstractMethodError(self)
 
     @classmethod
     def _simple_new(cls, values, **kwargs):
-        from pandas.errors import AbstractMethodError
         raise AbstractMethodError(cls)
 
     def _get_attributes_dict(self):
@@ -119,7 +118,7 @@ def _box_func(self):
         """
         box function to get object from internal representation
         """
-        raise com.AbstractMethodError(self)
+        raise AbstractMethodError(self)
 
     def _box_values(self, values):
         """
@@ -352,13 +351,13 @@ def _add_datelike(self, other):
                                 typ=type(other).__name__))
 
     def _sub_datelike(self, other):
-        raise com.AbstractMethodError(self)
+        raise AbstractMethodError(self)
 
     def _sub_period(self, other):
         return NotImplemented
 
     def _add_offset(self, offset):
-        raise com.AbstractMethodError(self)
+        raise AbstractMethodError(self)
 
     def _add_delta(self, other):
         return NotImplemented

From 42d3bdb1a88ad70d6a6262d99cd368a99ccfa348 Mon Sep 17 00:00:00 2001
From: Brock Mendel <jbrockmendel@gmail.com>
Date: Mon, 15 Oct 2018 16:43:16 -0700
Subject: [PATCH 03/11] remove unused try_cast kwarg

---
 pandas/core/frame.py        |  2 +-
 pandas/core/ops.py          | 17 +++++++----------
 pandas/core/sparse/frame.py |  2 +-
 3 files changed, 9 insertions(+), 12 deletions(-)

diff --git a/pandas/core/frame.py b/pandas/core/frame.py
index 729b9b23536e8..56402a86df224 100644
--- a/pandas/core/frame.py
+++ b/pandas/core/frame.py
@@ -4942,7 +4942,7 @@ def _combine_match_index(self, other, func, level=None):
                                      index=left.index, columns=self.columns,
                                      copy=False)
 
-    def _combine_match_columns(self, other, func, level=None, try_cast=True):
+    def _combine_match_columns(self, other, func, level=None):
         assert isinstance(other, Series)
         left, right = self.align(other, join='outer', axis=1, level=level,
                                  copy=False)
diff --git a/pandas/core/ops.py b/pandas/core/ops.py
index aff6f17fba2e2..111d27fdac5c9 100644
--- a/pandas/core/ops.py
+++ b/pandas/core/ops.py
@@ -1731,10 +1731,10 @@ def column_op(a, b):
 
 
 def _combine_series_frame(self, other, func, fill_value=None, axis=None,
-                          level=None, try_cast=True):
+                          level=None):
     """
     Apply binary operator `func` to self, other using alignment and fill
-    conventions determined by the fill_value, axis, level, and try_cast kwargs.
+    conventions determined by the fill_value, axis, and level kwargs.
 
     Parameters
     ----------
@@ -1744,7 +1744,6 @@ def _combine_series_frame(self, other, func, fill_value=None, axis=None,
     fill_value : object, default None
     axis : {0, 1, 'columns', 'index', None}, default None
     level : int or None, default None
-    try_cast : bool, default True
 
     Returns
     -------
@@ -1759,8 +1758,7 @@ def _combine_series_frame(self, other, func, fill_value=None, axis=None,
         if axis == 0:
             return self._combine_match_index(other, func, level=level)
         else:
-            return self._combine_match_columns(other, func, level=level,
-                                               try_cast=try_cast)
+            return self._combine_match_columns(other, func, level=level)
     else:
         if not len(other):
             return self * np.nan
@@ -1771,8 +1769,7 @@ def _combine_series_frame(self, other, func, fill_value=None, axis=None,
                                      columns=self.columns)
 
         # default axis is columns
-        return self._combine_match_columns(other, func, level=level,
-                                           try_cast=try_cast)
+        return self._combine_match_columns(other, func, level=level)
 
 
 def _align_method_FRAME(left, right, axis):
@@ -1872,7 +1869,7 @@ def f(self, other, axis=default_axis, level=None, fill_value=None):
             pass_op = op if axis in [0, "columns", None] else na_op
             return _combine_series_frame(self, other, pass_op,
                                          fill_value=fill_value, axis=axis,
-                                         level=level, try_cast=True)
+                                         level=level)
         else:
             if fill_value is not None:
                 self = self.fillna(fill_value)
@@ -1914,7 +1911,7 @@ def f(self, other, axis=default_axis, level=None):
         elif isinstance(other, ABCSeries):
             return _combine_series_frame(self, other, na_op,
                                          fill_value=None, axis=axis,
-                                         level=level, try_cast=False)
+                                         level=level)
         else:
             return self._combine_const(other, na_op, try_cast=False)
 
@@ -1939,7 +1936,7 @@ def f(self, other):
         elif isinstance(other, ABCSeries):
             return _combine_series_frame(self, other, func,
                                          fill_value=None, axis=None,
-                                         level=None, try_cast=False)
+                                         level=None)
         else:
 
             # straight boolean comparisons we want to allow all columns
diff --git a/pandas/core/sparse/frame.py b/pandas/core/sparse/frame.py
index 36b6ea089f459..0b536c1bdf7cd 100644
--- a/pandas/core/sparse/frame.py
+++ b/pandas/core/sparse/frame.py
@@ -618,7 +618,7 @@ def _combine_match_index(self, other, func, level=None):
             new_data, index=new_index, columns=self.columns,
             default_fill_value=fill_value).__finalize__(self)
 
-    def _combine_match_columns(self, other, func, level=None, try_cast=True):
+    def _combine_match_columns(self, other, func, level=None):
         # patched version of DataFrame._combine_match_columns to account for
         # NumPy circumventing __rsub__ with float64 types, e.g.: 3.0 - series,
         # where 3.0 is numpy.float64 and series is a SparseSeries. Still

From a9f6a230bdce75fbf6a8f7026231b3eb8f457cca Mon Sep 17 00:00:00 2001
From: Brock Mendel <jbrockmendel@gmail.com>
Date: Mon, 15 Oct 2018 16:45:26 -0700
Subject: [PATCH 04/11] avoid private constructor

---
 pandas/io/pytables.py | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/pandas/io/pytables.py b/pandas/io/pytables.py
index de193db846c50..0a2d34fec9496 100644
--- a/pandas/io/pytables.py
+++ b/pandas/io/pytables.py
@@ -2476,8 +2476,7 @@ def _get_index_factory(self, klass):
         if klass == DatetimeIndex:
             def f(values, freq=None, tz=None):
                 # data are already in UTC, localize and convert if tz present
-                result = DatetimeIndex._simple_new(values.values, name=None,
-                                                   freq=freq)
+                result = DatetimeIndex(values.values, name=None, freq=freq)
                 if tz is not None:
                     result = result.tz_localize('UTC').tz_convert(tz)
                 return result

From db44c4f22f65ec5d7abcc162c5bed4f2557ec76f Mon Sep 17 00:00:00 2001
From: Brock Mendel <jbrockmendel@gmail.com>
Date: Mon, 15 Oct 2018 16:47:55 -0700
Subject: [PATCH 05/11] Avoid need to override _generate_range in
 TimedeltaIndex

---
 pandas/core/arrays/timedeltas.py  |  6 ++----
 pandas/core/indexes/timedeltas.py | 20 ++++----------------
 2 files changed, 6 insertions(+), 20 deletions(-)

diff --git a/pandas/core/arrays/timedeltas.py b/pandas/core/arrays/timedeltas.py
index 4904a90ab7b2b..fe2d219f376f1 100644
--- a/pandas/core/arrays/timedeltas.py
+++ b/pandas/core/arrays/timedeltas.py
@@ -140,8 +140,7 @@ def __new__(cls, values, freq=None, start=None, end=None, periods=None,
         return result
 
     @classmethod
-    def _generate_range(cls, start, end, periods, freq, closed=None, **kwargs):
-        # **kwargs are for compat with TimedeltaIndex, which includes `name`
+    def _generate_range(cls, start, end, periods, freq, closed=None):
 
         periods = dtl.validate_periods(periods)
         if freq is None and any(x is None for x in [periods, start, end]):
@@ -167,10 +166,9 @@ def _generate_range(cls, start, end, periods, freq, closed=None, **kwargs):
 
         if freq is not None:
             index = _generate_regular_range(start, end, periods, freq)
-            index = cls._simple_new(index, freq=freq, **kwargs)
+            index = cls._simple_new(index, freq=freq)
         else:
             index = np.linspace(start.value, end.value, periods).astype('i8')
-            # TODO: shouldn't we pass `name` here?  (via **kwargs)
             index = cls._simple_new(index, freq=freq)
 
         if not left_closed:
diff --git a/pandas/core/indexes/timedeltas.py b/pandas/core/indexes/timedeltas.py
index 56b6dc7051d9f..ad380fd2e8544 100644
--- a/pandas/core/indexes/timedeltas.py
+++ b/pandas/core/indexes/timedeltas.py
@@ -147,12 +147,10 @@ def __new__(cls, data=None, unit=None, freq=None, start=None, end=None,
 
         if data is None:
             # TODO: Remove this block and associated kwargs; GH#20535
-            if freq is None and com._any_none(periods, start, end):
-                raise ValueError('Must provide freq argument if no data is '
-                                 'supplied')
-            periods = dtl.validate_periods(periods)
-            return cls._generate_range(start, end, periods, name, freq,
-                                       closed=closed)
+            result = cls._generate_range(start, end, periods, freq=freq,
+                                         closed=closed)
+            result.name = name
+            return result
 
         if unit is not None:
             data = to_timedelta(data, unit=unit, box=False)
@@ -181,16 +179,6 @@ def __new__(cls, data=None, unit=None, freq=None, start=None, end=None,
 
         return subarr
 
-    @classmethod
-    def _generate_range(cls, start, end, periods,
-                        name=None, freq=None, closed=None):
-        # TimedeltaArray gets `name` via **kwargs, so we need to explicitly
-        # override it if name is passed as a positional argument
-        return super(TimedeltaIndex, cls)._generate_range(start, end,
-                                                          periods, freq,
-                                                          name=name,
-                                                          closed=closed)
-
     @classmethod
     def _simple_new(cls, values, name=None, freq=None, **kwargs):
         result = super(TimedeltaIndex, cls)._simple_new(values, freq, **kwargs)

From f4b66c6f904dda902289f543f5fd10bed710ea53 Mon Sep 17 00:00:00 2001
From: Brock Mendel <jbrockmendel@gmail.com>
Date: Mon, 15 Oct 2018 16:49:34 -0700
Subject: [PATCH 06/11] Avoid overriding _generate_range in DatetimeINdex

---
 pandas/core/indexes/datetimes.py | 19 +++++--------------
 1 file changed, 5 insertions(+), 14 deletions(-)

diff --git a/pandas/core/indexes/datetimes.py b/pandas/core/indexes/datetimes.py
index e0219acc115b5..c9107d6509848 100644
--- a/pandas/core/indexes/datetimes.py
+++ b/pandas/core/indexes/datetimes.py
@@ -241,9 +241,11 @@ def __new__(cls, data=None,
 
         if data is None:
             # TODO: Remove this block and associated kwargs; GH#20535
-            return cls._generate_range(start, end, periods, name, freq,
-                                       tz=tz, normalize=normalize,
-                                       closed=closed, ambiguous=ambiguous)
+            result = cls._generate_range(start, end, periods,
+                                         freq=freq, tz=tz, normalize=normalize,
+                                         closed=closed, ambiguous=ambiguous)
+            result.name = name
+            return result
 
         if not isinstance(data, (np.ndarray, Index, ABCSeries,
                                  DatetimeArrayMixin)):
@@ -315,17 +317,6 @@ def __new__(cls, data=None,
 
         return subarr._deepcopy_if_needed(ref_to_data, copy)
 
-    @classmethod
-    @Appender(DatetimeArrayMixin._generate_range.__doc__)
-    def _generate_range(cls, start, end, periods, name=None, freq=None,
-                        tz=None, normalize=False, ambiguous='raise',
-                        closed=None):
-        out = super(DatetimeIndex, cls)._generate_range(
-            start, end, periods, freq,
-            tz=tz, normalize=normalize, ambiguous=ambiguous, closed=closed)
-        out.name = name
-        return out
-
     def _convert_for_op(self, value):
         """ Convert value to be insertable to ndarray """
         if self._has_same_tz(value):

From c376799756ed0da59570bf6b347742c0e4f2f60c Mon Sep 17 00:00:00 2001
From: Brock Mendel <jbrockmendel@gmail.com>
Date: Mon, 15 Oct 2018 16:54:08 -0700
Subject: [PATCH 07/11] get kwargs out of generate_range

---
 pandas/core/arrays/datetimelike.py  | 11 +++++++++--
 pandas/core/indexes/datetimelike.py |  6 ++++++
 pandas/core/indexes/period.py       |  2 --
 3 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/pandas/core/arrays/datetimelike.py b/pandas/core/arrays/datetimelike.py
index 7fbda6b4c1a1f..05572021dac3d 100644
--- a/pandas/core/arrays/datetimelike.py
+++ b/pandas/core/arrays/datetimelike.py
@@ -331,6 +331,10 @@ def _validate_frequency(cls, index, freq, **kwargs):
             # Frequency validation is not meaningful for Period Array/Index
             return None
 
+        # DatetimeArray may pass `ambiguous`, nothing else will be accepted
+        # by cls._generate_range below
+        assert all(key == 'ambiguous' for key in kwargs)
+
         inferred = index.inferred_freq
         if index.size == 0 or inferred == freq.freqstr:
             return None
@@ -594,9 +598,12 @@ def _time_shift(self, periods, freq=None):
 
         start = self[0] + periods * self.freq
         end = self[-1] + periods * self.freq
-        attribs = self._get_attributes_dict()
+
+        # Note: in the DatetimeTZ case, _generate_range will infer the
+        #  appropriate timezone from `start` and `end`, so tz does not need
+        #  to be passed explicitly.
         return self._generate_range(start=start, end=end, periods=None,
-                                    **attribs)
+                                    freq=self.freq)
 
     @classmethod
     def _add_datetimelike_methods(cls):
diff --git a/pandas/core/indexes/datetimelike.py b/pandas/core/indexes/datetimelike.py
index 8e919ba3599fc..eb8341f379f56 100644
--- a/pandas/core/indexes/datetimelike.py
+++ b/pandas/core/indexes/datetimelike.py
@@ -699,6 +699,12 @@ def astype(self, dtype, copy=True):
             raise TypeError(msg.format(name=type(self).__name__, dtype=dtype))
         return super(DatetimeIndexOpsMixin, self).astype(dtype, copy=copy)
 
+    @Appender(DatetimeLikeArrayMixin._time_shift.__doc__)
+    def _time_shift(self, periods, freq=None):
+        result = DatetimeLikeArrayMixin._time_shift(self, periods, freq=freq)
+        result.name = self.name
+        return result
+
 
 def _ensure_datetimelike_to_i8(other, to_utc=False):
     """
diff --git a/pandas/core/indexes/period.py b/pandas/core/indexes/period.py
index 64a70b52b02a6..137b93c19c386 100644
--- a/pandas/core/indexes/period.py
+++ b/pandas/core/indexes/period.py
@@ -165,8 +165,6 @@ def __new__(cls, data=None, ordinal=None, freq=None, start=None, end=None,
             raise TypeError('__new__() got an unexpected keyword argument {}'.
                             format(list(set(fields) - valid_field_set)[0]))
 
-        periods = dtl.validate_periods(periods)
-
         if name is None and hasattr(data, 'name'):
             name = data.name
 

From 47aebaec8736f986c719e4235ab357aa04cde383 Mon Sep 17 00:00:00 2001
From: Brock Mendel <jbrockmendel@gmail.com>
Date: Mon, 15 Oct 2018 16:55:48 -0700
Subject: [PATCH 08/11] more precise conditions

---
 pandas/core/arrays/datetimelike.py | 5 +++--
 pandas/core/arrays/period.py       | 2 +-
 2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/pandas/core/arrays/datetimelike.py b/pandas/core/arrays/datetimelike.py
index 05572021dac3d..59ac98391b727 100644
--- a/pandas/core/arrays/datetimelike.py
+++ b/pandas/core/arrays/datetimelike.py
@@ -332,8 +332,9 @@ def _validate_frequency(cls, index, freq, **kwargs):
             return None
 
         # DatetimeArray may pass `ambiguous`, nothing else will be accepted
-        # by cls._generate_range below
-        assert all(key == 'ambiguous' for key in kwargs)
+        #  by cls._generate_range below
+        acceptable = {'ambiguous'} if index.dtype.kind == 'M' else {}
+        assert all(key in acceptable for key in kwargs)
 
         inferred = index.inferred_freq
         if index.size == 0 or inferred == freq.freqstr:
diff --git a/pandas/core/arrays/period.py b/pandas/core/arrays/period.py
index 8624ddd8965e8..a4fdd6fcf49b8 100644
--- a/pandas/core/arrays/period.py
+++ b/pandas/core/arrays/period.py
@@ -180,7 +180,7 @@ def _generate_range(cls, start, end, periods, freq, fields):
             freq = Period._maybe_convert_freq(freq)
 
         field_count = len(fields)
-        if com.count_not_none(start, end) > 0:
+        if start is not None or end is not None:
             if field_count > 0:
                 raise ValueError('Can either instantiate from fields '
                                  'or endpoints, but not both')

From 44548291070f9284f55766c0837e8aa71d6fd565 Mon Sep 17 00:00:00 2001
From: Brock Mendel <jbrockmendel@gmail.com>
Date: Mon, 15 Oct 2018 16:59:37 -0700
Subject: [PATCH 09/11] move _maybe_convert_timedelta back to PeriodIndex

---
 pandas/core/arrays/period.py  | 45 +-------------------------------
 pandas/core/indexes/period.py | 48 +++++++++++++++++++++++++++++++++--
 2 files changed, 47 insertions(+), 46 deletions(-)

diff --git a/pandas/core/arrays/period.py b/pandas/core/arrays/period.py
index a4fdd6fcf49b8..ce54900898ea4 100644
--- a/pandas/core/arrays/period.py
+++ b/pandas/core/arrays/period.py
@@ -5,7 +5,6 @@
 
 import numpy as np
 
-from pandas._libs import lib
 from pandas._libs.tslib import NaT, iNaT
 from pandas._libs.tslibs.period import (
     Period, IncompatibleFrequency, DIFFERENT_FREQ_INDEX,
@@ -26,7 +25,7 @@
 import pandas.core.common as com
 
 from pandas.tseries import frequencies
-from pandas.tseries.offsets import Tick, DateOffset
+from pandas.tseries.offsets import Tick
 
 from pandas.core.arrays import datetimelike as dtl
 from pandas.core.arrays.datetimelike import DatetimeLikeArrayMixin
@@ -445,48 +444,6 @@ def _time_shift(self, n):
             values[self._isnan] = iNaT
         return self._shallow_copy(values=values)
 
-    def _maybe_convert_timedelta(self, other):
-        """
-        Convert timedelta-like input to an integer multiple of self.freq
-
-        Parameters
-        ----------
-        other : timedelta, np.timedelta64, DateOffset, int, np.ndarray
-
-        Returns
-        -------
-        converted : int, np.ndarray[int64]
-
-        Raises
-        ------
-        IncompatibleFrequency : if the input cannot be written as a multiple
-            of self.freq.  Note IncompatibleFrequency subclasses ValueError.
-        """
-        if isinstance(
-                other, (timedelta, np.timedelta64, Tick, np.ndarray)):
-            offset = frequencies.to_offset(self.freq.rule_code)
-            if isinstance(offset, Tick):
-                # _check_timedeltalike_freq_compat will raise if incompatible
-                delta = self._check_timedeltalike_freq_compat(other)
-                return delta
-        elif isinstance(other, DateOffset):
-            freqstr = other.rule_code
-            base = frequencies.get_base_alias(freqstr)
-            if base == self.freq.rule_code:
-                return other.n
-            msg = DIFFERENT_FREQ_INDEX.format(self.freqstr, other.freqstr)
-            raise IncompatibleFrequency(msg)
-        elif lib.is_integer(other):
-            # integer is passed to .shift via
-            # _add_datetimelike_methods basically
-            # but ufunc may pass integer to _add_delta
-            return other
-
-        # raise when input doesn't have freq
-        msg = "Input has different freq from {cls}(freq={freqstr})"
-        raise IncompatibleFrequency(msg.format(cls=type(self).__name__,
-                                               freqstr=self.freqstr))
-
     def _check_timedeltalike_freq_compat(self, other):
         """
         Arithmetic operations with timedelta-like scalars or array `other`
diff --git a/pandas/core/indexes/period.py b/pandas/core/indexes/period.py
index 137b93c19c386..8cb4d445bfe46 100644
--- a/pandas/core/indexes/period.py
+++ b/pandas/core/indexes/period.py
@@ -1,5 +1,5 @@
 # pylint: disable=E1101,E1103,W0232
-from datetime import datetime
+from datetime import datetime, timedelta
 import numpy as np
 import warnings
 
@@ -16,7 +16,9 @@
     pandas_dtype,
     ensure_object)
 
+from pandas.tseries import frequencies
 from pandas.tseries.frequencies import get_freq_code as _gfc
+from pandas.tseries.offsets import Tick, DateOffset
 
 from pandas.core.indexes.datetimes import DatetimeIndex, Int64Index, Index
 from pandas.core.indexes.datetimelike import (
@@ -25,7 +27,7 @@
 from pandas.core.tools.datetimes import parse_time_string
 
 from pandas._libs.lib import infer_dtype
-from pandas._libs import tslib, index as libindex
+from pandas._libs import lib, tslib, index as libindex
 from pandas._libs.tslibs.period import (Period, IncompatibleFrequency,
                                         DIFFERENT_FREQ_INDEX)
 from pandas._libs.tslibs import resolution, period
@@ -724,6 +726,48 @@ def __setstate__(self, state):
 
     _unpickle_compat = __setstate__
 
+    def _maybe_convert_timedelta(self, other):
+        """
+        Convert timedelta-like input to an integer multiple of self.freq
+
+        Parameters
+        ----------
+        other : timedelta, np.timedelta64, DateOffset, int, np.ndarray
+
+        Returns
+        -------
+        converted : int, np.ndarray[int64]
+
+        Raises
+        ------
+        IncompatibleFrequency : if the input cannot be written as a multiple
+            of self.freq.  Note IncompatibleFrequency subclasses ValueError.
+        """
+        if isinstance(
+                other, (timedelta, np.timedelta64, Tick, np.ndarray)):
+            offset = frequencies.to_offset(self.freq.rule_code)
+            if isinstance(offset, Tick):
+                # _check_timedeltalike_freq_compat will raise if incompatible
+                delta = self._check_timedeltalike_freq_compat(other)
+                return delta
+        elif isinstance(other, DateOffset):
+            freqstr = other.rule_code
+            base = frequencies.get_base_alias(freqstr)
+            if base == self.freq.rule_code:
+                return other.n
+            msg = DIFFERENT_FREQ_INDEX.format(self.freqstr, other.freqstr)
+            raise IncompatibleFrequency(msg)
+        elif lib.is_integer(other):
+            # integer is passed to .shift via
+            # _add_datetimelike_methods basically
+            # but ufunc may pass integer to _add_delta
+            return other
+
+        # raise when input doesn't have freq
+        msg = "Input has different freq from {cls}(freq={freqstr})"
+        raise IncompatibleFrequency(msg.format(cls=type(self).__name__,
+                                               freqstr=self.freqstr))
+
 
 PeriodIndex._add_comparison_ops()
 PeriodIndex._add_numeric_methods_disabled()

From cc1e3eb3fc43227a82bd4cecbbf19435b649c426 Mon Sep 17 00:00:00 2001
From: Brock Mendel <jbrockmendel@gmail.com>
Date: Mon, 15 Oct 2018 20:07:41 -0700
Subject: [PATCH 10/11] fixup missing validate_periods

---
 pandas/core/arrays/period.py | 1 +
 pandas/util/testing.py       | 2 +-
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/pandas/core/arrays/period.py b/pandas/core/arrays/period.py
index ce54900898ea4..9bd1590eb242e 100644
--- a/pandas/core/arrays/period.py
+++ b/pandas/core/arrays/period.py
@@ -175,6 +175,7 @@ def _from_ordinals(cls, values, freq=None, **kwargs):
 
     @classmethod
     def _generate_range(cls, start, end, periods, freq, fields):
+        periods = dtl.validate_periods(periods)
         if freq is not None:
             freq = Period._maybe_convert_freq(freq)
 
diff --git a/pandas/util/testing.py b/pandas/util/testing.py
index 1bd9043f42634..c02cd487e4c57 100644
--- a/pandas/util/testing.py
+++ b/pandas/util/testing.py
@@ -2483,7 +2483,7 @@ def wrapper(*args, **kwargs):
 
 def assert_raises_regex(_exception, _regexp, _callable=None,
                         *args, **kwargs):
-    """
+    r"""
     Check that the specified Exception is raised and that the error message
     matches a given regular expression pattern. This may be a regular
     expression object or a string containing a regular expression suitable

From 8d5539518754328fbc6b8b3c0a71b5563ed07249 Mon Sep 17 00:00:00 2001
From: Brock Mendel <jbrockmendel@gmail.com>
Date: Tue, 16 Oct 2018 11:44:25 -0700
Subject: [PATCH 11/11] port non-central parts of #22862

---
 pandas/core/accessor.py       | 11 ++++++-----
 pandas/core/arrays/base.py    |  2 +-
 pandas/core/indexes/base.py   |  3 +--
 pandas/tseries/frequencies.py |  1 +
 4 files changed, 9 insertions(+), 8 deletions(-)

diff --git a/pandas/core/accessor.py b/pandas/core/accessor.py
index eab529584d1fb..f2f8ae58dec56 100644
--- a/pandas/core/accessor.py
+++ b/pandas/core/accessor.py
@@ -68,7 +68,6 @@ def _add_delegate_accessors(cls, delegate, accessors, typ,
         overwrite : boolean, default False
            overwrite the method/property in the target class if it exists
         """
-
         def _create_delegator_property(name):
 
             def _getter(self):
@@ -107,9 +106,10 @@ def f(self, *args, **kwargs):
 
 def delegate_names(delegate, accessors, typ, overwrite=False):
     """
-    Add delegated names to a class using a class decorator.  This provides
-    an alternative usage to directly calling `_add_delegate_accessors`
-    below a class definition.
+    Add delegated names to a class using a class decorator.
+
+    This provides an alternative usage to directly calling
+    `_add_delegate_accessors` below a class definition.
 
     Parameters
     ----------
@@ -121,7 +121,8 @@ def delegate_names(delegate, accessors, typ, overwrite=False):
 
     Returns
     -------
-    decorator
+    callable
+        A class decorator
 
     Examples
     --------
diff --git a/pandas/core/arrays/base.py b/pandas/core/arrays/base.py
index b745569d5bd76..c18af21078ecf 100644
--- a/pandas/core/arrays/base.py
+++ b/pandas/core/arrays/base.py
@@ -122,7 +122,7 @@ def _from_factorized(cls, values, original):
         Parameters
         ----------
         values : ndarray
-            An integer ndarray with the factorized values.
+            An ndarray with the unique factorized values.
         original : ExtensionArray
             The original ExtensionArray that factorize was called on.
 
diff --git a/pandas/core/indexes/base.py b/pandas/core/indexes/base.py
index 51c84d6e28cb4..4da9dfc06889d 100644
--- a/pandas/core/indexes/base.py
+++ b/pandas/core/indexes/base.py
@@ -229,7 +229,7 @@ class Index(IndexOpsMixin, PandasObject):
     _outer_indexer = libjoin.outer_join_indexer_object
 
     _typ = 'index'
-    _data = None
+    _data = None  # type: Union[np.ndarray, ExtensionArray]
     _id = None
     name = None
     asi8 = None
@@ -261,7 +261,6 @@ def __new__(cls, data=None, dtype=None, copy=False, name=None,
             return cls._simple_new(data, name)
 
         from .range import RangeIndex
-
         # range
         if isinstance(data, RangeIndex):
             return RangeIndex(start=data, copy=copy, dtype=dtype, name=name)
diff --git a/pandas/tseries/frequencies.py b/pandas/tseries/frequencies.py
index d6e4824575468..22c7447768fff 100644
--- a/pandas/tseries/frequencies.py
+++ b/pandas/tseries/frequencies.py
@@ -233,6 +233,7 @@ def get_offset(name):
 
 
 def infer_freq(index, warn=True):
+    # type: (Union[Series, Index, PeriodArray]) -> Freq
     """
     Infer the most likely frequency given the input index. If the frequency is
     uncertain, a warning will be printed.