From 1ea71f8649725327c13435c882f1f65f4c063b8b Mon Sep 17 00:00:00 2001
From: MomIsBestFriend <>
Date: Sat, 8 Feb 2020 15:38:46 +0200
Subject: [PATCH 1/8] CLN: some code cleanups in pandas/_libs/

---
 pandas/_libs/algos.pyx            | 31 ++++++++++----
 pandas/_libs/join.pyx             | 20 +++++++--
 pandas/_libs/lib.pyx              | 70 ++++++++++++++++++-------------
 pandas/_libs/reshape.pyx          | 20 +++++++--
 pandas/_libs/sparse.pyx           |  4 +-
 pandas/_libs/tslibs/period.pyx    | 63 +++++++++++++++-------------
 pandas/_libs/tslibs/strptime.pyx  | 11 ++---
 pandas/_libs/tslibs/timezones.pyx |  4 +-
 8 files changed, 139 insertions(+), 84 deletions(-)

diff --git a/pandas/_libs/algos.pyx b/pandas/_libs/algos.pyx
index dd1f38ce3a842..ec66683a906cc 100644
--- a/pandas/_libs/algos.pyx
+++ b/pandas/_libs/algos.pyx
@@ -7,13 +7,30 @@ from libc.math cimport fabs, sqrt
 
 import numpy as np
 cimport numpy as cnp
-from numpy cimport (ndarray,
-                    NPY_INT64, NPY_INT32, NPY_INT16, NPY_INT8,
-                    NPY_UINT64, NPY_UINT32, NPY_UINT16, NPY_UINT8,
-                    NPY_FLOAT32, NPY_FLOAT64,
-                    NPY_OBJECT,
-                    int8_t, int16_t, int32_t, int64_t, uint8_t, uint16_t,
-                    uint32_t, uint64_t, float32_t, float64_t)
+from numpy cimport (
+    NPY_FLOAT32,
+    NPY_FLOAT64,
+    NPY_INT8,
+    NPY_INT16,
+    NPY_INT32,
+    NPY_INT64,
+    NPY_OBJECT,
+    NPY_UINT8,
+    NPY_UINT16,
+    NPY_UINT32,
+    NPY_UINT64,
+    float32_t,
+    float64_t,
+    int8_t,
+    int16_t,
+    int32_t,
+    int64_t,
+    ndarray,
+    uint8_t,
+    uint16_t,
+    uint32_t,
+    uint64_t,
+)
 cnp.import_array()
 
 
diff --git a/pandas/_libs/join.pyx b/pandas/_libs/join.pyx
index 093c53790cd35..dfa7aa708d681 100644
--- a/pandas/_libs/join.pyx
+++ b/pandas/_libs/join.pyx
@@ -3,13 +3,25 @@ from cython import Py_ssize_t
 
 import numpy as np
 cimport numpy as cnp
-from numpy cimport (ndarray,
-                    int8_t, int16_t, int32_t, int64_t, uint8_t, uint16_t,
-                    uint32_t, uint64_t, float32_t, float64_t)
+from numpy cimport (
+    float32_t,
+    float64_t,
+    int8_t,
+    int16_t,
+    int32_t,
+    int64_t,
+    ndarray,
+    uint8_t,
+    uint16_t,
+    uint32_t,
+    uint64_t,
+)
 cnp.import_array()
 
 from pandas._libs.algos import (
-    groupsort_indexer, ensure_platform_int, take_1d_int64_int64
+    ensure_platform_int,
+    groupsort_indexer,
+    take_1d_int64_int64,
 )
 
 
diff --git a/pandas/_libs/lib.pyx b/pandas/_libs/lib.pyx
index 9702eb4615909..8a62282fbb8c3 100644
--- a/pandas/_libs/lib.pyx
+++ b/pandas/_libs/lib.pyx
@@ -15,18 +15,33 @@ from cpython.iterator cimport PyIter_Check
 from cpython.sequence cimport PySequence_Check
 from cpython.number cimport PyNumber_Check
 
-from cpython.datetime cimport (PyDateTime_Check, PyDate_Check,
-                               PyTime_Check, PyDelta_Check,
-                               PyDateTime_IMPORT)
+from cpython.datetime cimport (
+    PyDateTime_Check,
+    PyDate_Check,
+    PyTime_Check,
+    PyDelta_Check,
+    PyDateTime_IMPORT
+)
 PyDateTime_IMPORT
 
 import numpy as np
 cimport numpy as cnp
-from numpy cimport (ndarray, PyArray_Check, PyArray_GETITEM,
-                    PyArray_ITER_DATA, PyArray_ITER_NEXT, PyArray_IterNew,
-                    flatiter, NPY_OBJECT,
-                    int64_t, float32_t, float64_t,
-                    uint8_t, uint64_t, complex128_t)
+from numpy cimport (
+    NPY_OBJECT,
+    PyArray_Check,
+    PyArray_GETITEM,
+    PyArray_ITER_DATA,
+    PyArray_ITER_NEXT,
+    PyArray_IterNew,
+    complex128_t,
+    flatiter,
+    float32_t,
+    float64_t,
+    int64_t,
+    ndarray,
+    uint8_t,
+    uint64_t,
+)
 cnp.import_array()
 
 cdef extern from "numpy/arrayobject.h":
@@ -60,7 +75,12 @@ from pandas._libs.tslibs.timedeltas cimport convert_to_timedelta64
 from pandas._libs.tslibs.timezones cimport get_timezone, tz_compare
 
 from pandas._libs.missing cimport (
-    checknull, isnaobj, is_null_datetime64, is_null_timedelta64, is_null_period, C_NA
+    checknull,
+    isnaobj,
+    is_null_datetime64,
+    is_null_timedelta64,
+    is_null_period,
+    C_NA
 )
 
 
@@ -98,14 +118,11 @@ def memory_usage_of_objects(arr: object[:]) -> int64_t:
 
     Does not include the actual bytes of the pointers
     """
-    i: Py_ssize_t
-    n: Py_ssize_t
     size: int64_t
 
     size = 0
-    n = len(arr)
-    for i in range(n):
-        size += arr[i].__sizeof__()
+    for value in arr:
+        size += value.__sizeof__()
     return size
 
 
@@ -246,7 +263,7 @@ def item_from_zerodim(val: object) -> object:
 
 @cython.wraparound(False)
 @cython.boundscheck(False)
-def fast_unique_multiple(list arrays, sort: bool=True):
+def fast_unique_multiple(list arrays, bint sort=True):
     """
     Generate a list of unique values from a list of arrays.
 
@@ -262,21 +279,18 @@ def fast_unique_multiple(list arrays, sort: bool=True):
     list of unique values
     """
     cdef:
-        ndarray[object] buf
-        Py_ssize_t k = len(arrays)
-        Py_ssize_t i, j, n
+        ndarray[object] buf_array
         list uniques = []
         dict table = {}
-        object val, stub = 0
+        object value, stub = 0
+
+
+    for buf_array in arrays:
+        for value in buf_array:
+            if value not in table:
+                table[value] = stub
+                uniques.append(value)
 
-    for i in range(k):
-        buf = arrays[i]
-        n = len(buf)
-        for j in range(n):
-            val = buf[j]
-            if val not in table:
-                table[val] = stub
-                uniques.append(val)
     if sort is None:
         try:
             uniques.sort()
@@ -289,7 +303,7 @@ def fast_unique_multiple(list arrays, sort: bool=True):
 
 @cython.wraparound(False)
 @cython.boundscheck(False)
-def fast_unique_multiple_list(lists: list, sort: bool=True) -> list:
+def fast_unique_multiple_list(lists: list, bint sort=True) -> list:
     cdef:
         list buf
         Py_ssize_t k = len(lists)
diff --git a/pandas/_libs/reshape.pyx b/pandas/_libs/reshape.pyx
index 4e831081c8e54..6af5caafa5ea8 100644
--- a/pandas/_libs/reshape.pyx
+++ b/pandas/_libs/reshape.pyx
@@ -1,8 +1,20 @@
 import cython
 from cython import Py_ssize_t
 
-from numpy cimport (int8_t, int16_t, int32_t, int64_t, uint8_t, uint16_t,
-                    uint32_t, uint64_t, float32_t, float64_t, ndarray)
+from numpy cimport (
+    float32_t,
+    float64_t,
+    int8_t,
+    int16_t,
+    int32_t,
+    int64_t,
+    ndarray,
+    uint8_t,
+    uint16_t,
+    uint32_t,
+    uint64_t,
+)
+
 cimport numpy as cnp
 import numpy as np
 from pandas._libs.lib cimport c_is_list_like
@@ -125,8 +137,8 @@ def explode(ndarray[object] values):
 
         if c_is_list_like(v, False):
             if len(v):
-                for j in range(len(v)):
-                    result[count] = v[j]
+                for value in v:
+                    result[count] = value
                     count += 1
             else:
                 # empty list-like, use a nan marker
diff --git a/pandas/_libs/sparse.pyx b/pandas/_libs/sparse.pyx
index 3a6dd506b2428..4ca053a0ee83a 100644
--- a/pandas/_libs/sparse.pyx
+++ b/pandas/_libs/sparse.pyx
@@ -448,7 +448,7 @@ cdef class BlockIndex(SparseIndex):
         ylen = y.blengths
 
         # block may be split, but can't exceed original len / 2 + 1
-        max_len = int(min(self.length, y.length) / 2) + 1
+        max_len = min(self.length, y.length) // 2 + 1
         out_bloc = np.empty(max_len, dtype=np.int32)
         out_blen = np.empty(max_len, dtype=np.int32)
 
@@ -672,7 +672,7 @@ cdef class BlockUnion(BlockMerge):
         ystart = self.ystart
         yend = self.yend
 
-        max_len = int(min(self.x.length, self.y.length) / 2) + 1
+        max_len = min(self.x.length, self.y.length) // 2 + 1
         out_bloc = np.empty(max_len, dtype=np.int32)
         out_blen = np.empty(max_len, dtype=np.int32)
 
diff --git a/pandas/_libs/tslibs/period.pyx b/pandas/_libs/tslibs/period.pyx
index 9419f0eba39aa..39ff106e235b1 100644
--- a/pandas/_libs/tslibs/period.pyx
+++ b/pandas/_libs/tslibs/period.pyx
@@ -1,8 +1,6 @@
 from datetime import datetime
 
-from cpython.object cimport (
-    PyObject_RichCompareBool,
-    Py_EQ, Py_NE)
+from cpython.object cimport PyObject_RichCompareBool, Py_EQ, Py_NE
 
 from numpy cimport int64_t, import_array, ndarray
 import numpy as np
@@ -14,15 +12,25 @@ from libc.string cimport strlen, memset
 
 import cython
 
-from cpython.datetime cimport (PyDateTime_Check, PyDelta_Check, PyDate_Check,
-                               PyDateTime_IMPORT)
+from cpython.datetime cimport (
+    PyDate_Check,
+    PyDateTime_Check,
+    PyDateTime_IMPORT,
+    PyDelta_Check,
+)
 # import datetime C API
 PyDateTime_IMPORT
 
 from pandas._libs.tslibs.np_datetime cimport (
-    npy_datetimestruct, dtstruct_to_dt64, dt64_to_dtstruct,
-    pandas_datetime_to_datetimestruct, check_dts_bounds,
-    NPY_DATETIMEUNIT, NPY_FR_D, NPY_FR_us)
+    npy_datetimestruct,
+    dtstruct_to_dt64,
+    dt64_to_dtstruct,
+    pandas_datetime_to_datetimestruct,
+    check_dts_bounds,
+    NPY_DATETIMEUNIT,
+    NPY_FR_D,
+    NPY_FR_us
+)
 
 cdef extern from "src/datetime/np_datetime.h":
     int64_t npy_datetimestruct_to_datetime(NPY_DATETIMEUNIT fr,
@@ -37,12 +45,15 @@ from pandas._libs.tslibs.timedeltas import Timedelta
 from pandas._libs.tslibs.timedeltas cimport delta_to_nanoseconds
 
 cimport pandas._libs.tslibs.ccalendar as ccalendar
-from pandas._libs.tslibs.ccalendar cimport (
-    dayofweek, get_day_of_year, is_leapyear)
+from pandas._libs.tslibs.ccalendar cimport dayofweek, get_day_of_year, is_leapyear
 from pandas._libs.tslibs.ccalendar import MONTH_NUMBERS
 from pandas._libs.tslibs.frequencies cimport (
-    get_freq_code, get_base_alias, get_to_timestamp_base, get_freq_str,
-    get_rule_month)
+    get_base_alias,
+    get_freq_code,
+    get_freq_str,
+    get_rule_month,
+    get_to_timestamp_base,
+)
 from pandas._libs.tslibs.parsing import parse_time_string
 from pandas._libs.tslibs.resolution import Resolution
 from pandas._libs.tslibs.nattype import nat_strings
@@ -55,7 +66,7 @@ from pandas._libs.tslibs.tzconversion cimport tz_convert_utc_to_tzlocal
 
 cdef:
     enum:
-        INT32_MIN = -2147483648
+        INT32_MIN = -2_147_483_648
 
 
 ctypedef struct asfreq_info:
@@ -131,9 +142,7 @@ cdef int64_t get_daytime_conversion_factor(int from_index, int to_index) nogil:
         int col = max_value(from_index, to_index)
     # row or col < 6 means frequency strictly lower than Daily, which
     # do not use daytime_conversion_factors
-    if row < 6:
-        return 0
-    elif col < 6:
+    if row < 6 or col < 6:
         return 0
     return daytime_conversion_factor_matrix[row - 6][col - 6]
 
@@ -179,8 +188,7 @@ cdef freq_conv_func get_asfreq_func(int from_freq, int to_freq) nogil:
             return <freq_conv_func>asfreq_MtoB
         elif from_group == FR_WK:
             return <freq_conv_func>asfreq_WtoB
-        elif from_group in [FR_DAY, FR_HR, FR_MIN, FR_SEC,
-                            FR_MS, FR_US, FR_NS]:
+        elif from_group in [FR_DAY, FR_HR, FR_MIN, FR_SEC, FR_MS, FR_US, FR_NS]:
             return <freq_conv_func>asfreq_DTtoB
         else:
             return <freq_conv_func>nofunc
@@ -289,17 +297,15 @@ cdef int64_t DtoB(npy_datetimestruct *dts, int roll_back,
     return DtoB_weekday(unix_date)
 
 
-cdef inline int64_t upsample_daytime(int64_t ordinal,
-                                     asfreq_info *af_info) nogil:
+cdef inline int64_t upsample_daytime(int64_t ordinal, asfreq_info *af_info) nogil:
     if (af_info.is_end):
         return (ordinal + 1) * af_info.intraday_conversion_factor - 1
     else:
         return ordinal * af_info.intraday_conversion_factor
 
 
-cdef inline int64_t downsample_daytime(int64_t ordinal,
-                                       asfreq_info *af_info) nogil:
-    return ordinal // (af_info.intraday_conversion_factor)
+cdef inline int64_t downsample_daytime(int64_t ordinal, asfreq_info *af_info) nogil:
+    return ordinal // af_info.intraday_conversion_factor
 
 
 cdef inline int64_t transform_via_day(int64_t ordinal,
@@ -1463,16 +1469,13 @@ def extract_freq(ndarray[object] values):
     # TODO: Change type to const object[:] when Cython supports that.
 
     cdef:
-        Py_ssize_t i, n = len(values)
-        object p
-
-    for i in range(n):
-        p = values[i]
+        object value
 
+    for value in values:
         try:
             # now Timestamp / NaT has freq attr
-            if is_period_object(p):
-                return p.freq
+            if is_period_object(value):
+                return value.freq
         except AttributeError:
             pass
 
diff --git a/pandas/_libs/tslibs/strptime.pyx b/pandas/_libs/tslibs/strptime.pyx
index 5508b208de00a..396d5ca9ee35d 100644
--- a/pandas/_libs/tslibs/strptime.pyx
+++ b/pandas/_libs/tslibs/strptime.pyx
@@ -45,8 +45,7 @@ cdef dict _parse_code_table = {'y': 0,
                                'u': 22}
 
 
-def array_strptime(object[:] values, object fmt,
-                   bint exact=True, errors='raise'):
+def array_strptime(object[:] values, object fmt, bint exact=True, errors='raise'):
     """
     Calculates the datetime structs represented by the passed array of strings
 
@@ -78,12 +77,10 @@ def array_strptime(object[:] values, object fmt,
     if fmt is not None:
         if '%W' in fmt or '%U' in fmt:
             if '%Y' not in fmt and '%y' not in fmt:
-                raise ValueError("Cannot use '%W' or '%U' without "
-                                 "day and year")
+                raise ValueError("Cannot use '%W' or '%U' without day and year")
             if ('%A' not in fmt and '%a' not in fmt and '%w' not
                     in fmt):
-                raise ValueError("Cannot use '%W' or '%U' without "
-                                 "day and year")
+                raise ValueError("Cannot use '%W' or '%U' without day and year")
         elif '%Z' in fmt and '%z' in fmt:
             raise ValueError("Cannot parse both %Z and %z")
 
@@ -749,6 +746,6 @@ cdef parse_timezone_directive(str z):
     microseconds = int(gmtoff_remainder + gmtoff_remainder_padding)
 
     total_minutes = ((hours * 60) + minutes + (seconds // 60) +
-                     (microseconds // 60000000))
+                     (microseconds // 60_000_000))
     total_minutes = -total_minutes if z.startswith("-") else total_minutes
     return pytz.FixedOffset(total_minutes)
diff --git a/pandas/_libs/tslibs/timezones.pyx b/pandas/_libs/tslibs/timezones.pyx
index 35ee87e714fa8..07947f6677c04 100644
--- a/pandas/_libs/tslibs/timezones.pyx
+++ b/pandas/_libs/tslibs/timezones.pyx
@@ -196,7 +196,7 @@ cdef int64_t[:] unbox_utcoffsets(object transinfo):
     arr = np.empty(sz, dtype='i8')
 
     for i in range(sz):
-        arr[i] = int(transinfo[i][0].total_seconds()) * 1000000000
+        arr[i] = int(transinfo[i][0].total_seconds()) * 1_000_000_000
 
     return arr
 
@@ -217,7 +217,7 @@ cdef object get_dst_info(object tz):
     if cache_key is None:
         # e.g. pytz.FixedOffset, matplotlib.dates._UTC,
         # psycopg2.tz.FixedOffsetTimezone
-        num = int(get_utcoffset(tz, None).total_seconds()) * 1000000000
+        num = int(get_utcoffset(tz, None).total_seconds()) * 1_000_000_000
         return (np.array([NPY_NAT + 1], dtype=np.int64),
                 np.array([num], dtype=np.int64),
                 None)

From 8634a370129df78ea0670b07cf385be8c03ba1e4 Mon Sep 17 00:00:00 2001
From: MomIsBestFriend <>
Date: Fri, 14 Feb 2020 16:05:19 +0200
Subject: [PATCH 2/8] Reverted "bint"

REF:
https://github.com/pandas-dev/pandas/pull/31808/files#r376721172
---
 pandas/_libs/lib.pyx | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/pandas/_libs/lib.pyx b/pandas/_libs/lib.pyx
index c6f4cd0e893ff..cb846055edf25 100644
--- a/pandas/_libs/lib.pyx
+++ b/pandas/_libs/lib.pyx
@@ -263,7 +263,7 @@ def item_from_zerodim(val: object) -> object:
 
 @cython.wraparound(False)
 @cython.boundscheck(False)
-def fast_unique_multiple(list arrays, bint sort=True):
+def fast_unique_multiple(list arrays, sort: bool = True):
     """
     Generate a list of unique values from a list of arrays.
 
@@ -303,7 +303,7 @@ def fast_unique_multiple(list arrays, bint sort=True):
 
 @cython.wraparound(False)
 @cython.boundscheck(False)
-def fast_unique_multiple_list(lists: list, bint sort=True) -> list:
+def fast_unique_multiple_list(lists: list, sort: bool = True) -> list:
     cdef:
         list buf
         Py_ssize_t k = len(lists)

From 362e1f728b5b010817ed6f6ffb2b5c7d9b664510 Mon Sep 17 00:00:00 2001
From: MomIsBestFriend <>
Date: Fri, 14 Feb 2020 16:18:32 +0200
Subject: [PATCH 3/8] Added trailing comma to imports

REF:
https://github.com/pandas-dev/pandas/pull/31808/files#r378523656
---
 pandas/_libs/lib.pyx           | 4 ++--
 pandas/_libs/tslibs/period.pyx | 2 +-
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/pandas/_libs/lib.pyx b/pandas/_libs/lib.pyx
index cb846055edf25..b012e58af2a92 100644
--- a/pandas/_libs/lib.pyx
+++ b/pandas/_libs/lib.pyx
@@ -20,7 +20,7 @@ from cpython.datetime cimport (
     PyDate_Check,
     PyTime_Check,
     PyDelta_Check,
-    PyDateTime_IMPORT
+    PyDateTime_IMPORT,
 )
 PyDateTime_IMPORT
 
@@ -80,7 +80,7 @@ from pandas._libs.missing cimport (
     is_null_datetime64,
     is_null_timedelta64,
     is_null_period,
-    C_NA
+    C_NA,
 )
 
 
diff --git a/pandas/_libs/tslibs/period.pyx b/pandas/_libs/tslibs/period.pyx
index 39ff106e235b1..0970b2782e02f 100644
--- a/pandas/_libs/tslibs/period.pyx
+++ b/pandas/_libs/tslibs/period.pyx
@@ -29,7 +29,7 @@ from pandas._libs.tslibs.np_datetime cimport (
     check_dts_bounds,
     NPY_DATETIMEUNIT,
     NPY_FR_D,
-    NPY_FR_us
+    NPY_FR_us,
 )
 
 cdef extern from "src/datetime/np_datetime.h":

From e1511839120fdcf0bd3397b1745e51bb92d91166 Mon Sep 17 00:00:00 2001
From: MomIsBestFriend <>
Date: Fri, 14 Feb 2020 16:32:12 +0200
Subject: [PATCH 4/8] Reverted bad code

---
 pandas/_libs/lib.pyx           | 27 +++++++++++++++++----------
 pandas/_libs/reshape.pyx       |  4 ++--
 pandas/_libs/tslibs/period.pyx |  6 ++++--
 3 files changed, 23 insertions(+), 14 deletions(-)

diff --git a/pandas/_libs/lib.pyx b/pandas/_libs/lib.pyx
index b012e58af2a92..7a18429f21a18 100644
--- a/pandas/_libs/lib.pyx
+++ b/pandas/_libs/lib.pyx
@@ -118,11 +118,14 @@ def memory_usage_of_objects(arr: object[:]) -> int64_t:
 
     Does not include the actual bytes of the pointers
     """
+    i: Py_ssize_t
+    n: Py_ssize_t
     size: int64_t
 
     size = 0
-    for value in arr:
-        size += value.__sizeof__()
+    n = len(arr)
+    for i in range(n):
+        size += arr[i].__sizeof__()
     return size
 
 
@@ -279,17 +282,21 @@ def fast_unique_multiple(list arrays, sort: bool = True):
     list of unique values
     """
     cdef:
-        ndarray[object] buf_array
+        ndarray[object] buf
+        Py_ssize_t k = len(arrays)
+        Py_ssize_t i, j, n
         list uniques = []
         dict table = {}
-        object value, stub = 0
-
+        object val, stub = 0
 
-    for buf_array in arrays:
-        for value in buf_array:
-            if value not in table:
-                table[value] = stub
-                uniques.append(value)
+    for i in range(k):
+        buf = arrays[i]
+        n = len(buf)
+        for j in range(n):
+            val = buf[j]
+            if val not in table:
+                table[val] = stub
+                uniques.append(val)
 
     if sort is None:
         try:
diff --git a/pandas/_libs/reshape.pyx b/pandas/_libs/reshape.pyx
index 6af5caafa5ea8..e74b5919a4590 100644
--- a/pandas/_libs/reshape.pyx
+++ b/pandas/_libs/reshape.pyx
@@ -137,8 +137,8 @@ def explode(ndarray[object] values):
 
         if c_is_list_like(v, False):
             if len(v):
-                for value in v:
-                    result[count] = value
+                for j in range(len(v)):
+                    result[count] = v[j]
                     count += 1
             else:
                 # empty list-like, use a nan marker
diff --git a/pandas/_libs/tslibs/period.pyx b/pandas/_libs/tslibs/period.pyx
index 0970b2782e02f..7d383c54cb7ae 100644
--- a/pandas/_libs/tslibs/period.pyx
+++ b/pandas/_libs/tslibs/period.pyx
@@ -1469,9 +1469,12 @@ def extract_freq(ndarray[object] values):
     # TODO: Change type to const object[:] when Cython supports that.
 
     cdef:
+        Py_ssize_t i, n = len(values)
         object value
 
-    for value in values:
+    for i in range(n):
+        value = values[i]
+
         try:
             # now Timestamp / NaT has freq attr
             if is_period_object(value):
@@ -1481,7 +1484,6 @@ def extract_freq(ndarray[object] values):
 
     raise ValueError('freq not specified and cannot be inferred')
 
-
 # -----------------------------------------------------------------------
 # period helpers
 

From b369447298dfec91576db6df57ed4b1d27d83ecc Mon Sep 17 00:00:00 2001
From: MomIsBestFriend <>
Date: Sat, 15 Feb 2020 10:36:34 +0200
Subject: [PATCH 5/8] Lint issues

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

diff --git a/pandas/_libs/tslibs/period.pyx b/pandas/_libs/tslibs/period.pyx
index 7d383c54cb7ae..f63fc39738f64 100644
--- a/pandas/_libs/tslibs/period.pyx
+++ b/pandas/_libs/tslibs/period.pyx
@@ -1487,6 +1487,7 @@ def extract_freq(ndarray[object] values):
 # -----------------------------------------------------------------------
 # period helpers
 
+
 @cython.wraparound(False)
 @cython.boundscheck(False)
 cdef int64_t[:] localize_dt64arr_to_period(const int64_t[:] stamps,

From 208bc03d269125cb5ba99f4cc46a7be41755d4b5 Mon Sep 17 00:00:00 2001
From: MomIsBestFriend <>
Date: Sat, 15 Feb 2020 12:19:43 +0200
Subject: [PATCH 6/8] Reverted wrong code

REF:
https://github.com/pandas-dev/pandas/pull/31808#discussion_r379806862
---
 pandas/_libs/tslibs/period.pyx | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/pandas/_libs/tslibs/period.pyx b/pandas/_libs/tslibs/period.pyx
index f63fc39738f64..0287d1c97c458 100644
--- a/pandas/_libs/tslibs/period.pyx
+++ b/pandas/_libs/tslibs/period.pyx
@@ -142,7 +142,9 @@ cdef int64_t get_daytime_conversion_factor(int from_index, int to_index) nogil:
         int col = max_value(from_index, to_index)
     # row or col < 6 means frequency strictly lower than Daily, which
     # do not use daytime_conversion_factors
-    if row < 6 or col < 6:
+    if row < 6:
+        return 0
+    elif col < 6:
         return 0
     return daytime_conversion_factor_matrix[row - 6][col - 6]
 

From 0b47e28ca088cc8f57b7e711d158530d3539c45c Mon Sep 17 00:00:00 2001
From: MomIsBestFriend <>
Date: Sat, 22 Feb 2020 12:25:43 +0200
Subject: [PATCH 7/8] Removed parens

REF:
https://github.com/pandas-dev/pandas/pull/31808#discussion_r381626183
---
 pandas/_libs/tslibs/period.pyx | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pandas/_libs/tslibs/period.pyx b/pandas/_libs/tslibs/period.pyx
index 0287d1c97c458..c3a47902cff0f 100644
--- a/pandas/_libs/tslibs/period.pyx
+++ b/pandas/_libs/tslibs/period.pyx
@@ -300,7 +300,7 @@ cdef int64_t DtoB(npy_datetimestruct *dts, int roll_back,
 
 
 cdef inline int64_t upsample_daytime(int64_t ordinal, asfreq_info *af_info) nogil:
-    if (af_info.is_end):
+    if af_info.is_end:
         return (ordinal + 1) * af_info.intraday_conversion_factor - 1
     else:
         return ordinal * af_info.intraday_conversion_factor

From eaf2d49a87ac5fc962b5a82e4484d57c6c8c8ab3 Mon Sep 17 00:00:00 2001
From: MomIsBestFriend <>
Date: Sat, 22 Feb 2020 12:27:52 +0200
Subject: [PATCH 8/8] "in fmt" in prev line

REF:
https://github.com/pandas-dev/pandas/pull/31808#discussion_r381626633
---
 pandas/_libs/tslibs/strptime.pyx | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/pandas/_libs/tslibs/strptime.pyx b/pandas/_libs/tslibs/strptime.pyx
index 396d5ca9ee35d..dfe050c7bbff7 100644
--- a/pandas/_libs/tslibs/strptime.pyx
+++ b/pandas/_libs/tslibs/strptime.pyx
@@ -78,8 +78,7 @@ def array_strptime(object[:] values, object fmt, bint exact=True, errors='raise'
         if '%W' in fmt or '%U' in fmt:
             if '%Y' not in fmt and '%y' not in fmt:
                 raise ValueError("Cannot use '%W' or '%U' without day and year")
-            if ('%A' not in fmt and '%a' not in fmt and '%w' not
-                    in fmt):
+            if '%A' not in fmt and '%a' not in fmt and '%w' not in fmt:
                 raise ValueError("Cannot use '%W' or '%U' without day and year")
         elif '%Z' in fmt and '%z' in fmt:
             raise ValueError("Cannot parse both %Z and %z")