PERF: Use ccalendar.get_days_in_month over tslib.monthrange

pandas/_libs/tslib.pyx

@@ -25,9 +25,7 @@ from tslibs.np_datetime cimport (check_dts_bounds,
                                  _string_to_dts,
                                  dt64_to_dtstruct, dtstruct_to_dt64,
                                  pydatetime_to_dt64, pydate_to_dt64,
-                                 get_datetime64_value,
-                                 days_per_month_table,
-                                 dayofweek, is_leapyear)
+                                 get_datetime64_value)
 from tslibs.np_datetime import OutOfBoundsDatetime
 
 from tslibs.parsing import parse_datetime_string
@@ -763,18 +761,6 @@ cdef inline bint _parse_today_now(str val, int64_t* iresult):
 # Some general helper functions
 
 
-def monthrange(int64_t year, int64_t month):
-    cdef:
-        int64_t days
-
-    if month < 1 or month > 12:
-        raise ValueError("bad month number 0; must be 1-12")
-
-    days = days_per_month_table[is_leapyear(year)][month - 1]
-
-    return (dayofweek(year, month, 1), days)
-
-
 cpdef normalize_date(object dt):
     """
     Normalize datetime.datetime value to midnight. Returns datetime.date as a

pandas/_libs/tslibs/resolution.pyx

@@ -25,6 +25,7 @@ from fields import build_field_sarray
 from conversion import tz_convert
 from conversion cimport tz_convert_utc_to_tzlocal
 from ccalendar import MONTH_ALIASES, int_to_weekday
+from ccalendar cimport get_days_in_month
 
 from pandas._libs.properties import cache_readonly
 from pandas._libs.tslib import Timestamp
@@ -487,7 +488,6 @@ class _FrequencyInferer(object):
         days = self.fields['D']
         weekdays = self.index.dayofweek
 
-        from calendar import monthrange
         for y, m, d, wd in zip(years, months, days, weekdays):
 
             if calendar_start:
@@ -496,7 +496,7 @@ class _FrequencyInferer(object):
                 business_start &= d == 1 or (d <= 3 and wd == 0)
 
             if calendar_end or business_end:
-                _, daysinmonth = monthrange(y, m)
+                daysinmonth = get_days_in_month(y, m)
                 cal = d == daysinmonth
                 if calendar_end:
                     calendar_end &= cal

pandas/core/indexes/datetimes.py

@@ -55,6 +55,7 @@
 from pandas._libs import (lib, index as libindex, tslib as libts,
                           join as libjoin, Timestamp)
 from pandas._libs.tslibs import (timezones, conversion, fields, parsing,
+                                 ccalendar,
                                  resolution as libresolution)
 
 # -------- some conversion wrapper functions
@@ -1451,14 +1452,14 @@ def _parsed_string_to_bounds(self, reso, parsed):
                     Timestamp(datetime(parsed.year, 12, 31, 23,
                                        59, 59, 999999), tz=self.tz))
         elif reso == 'month':
-            d = libts.monthrange(parsed.year, parsed.month)[1]
+            d = ccalendar.get_days_in_month(parsed.year, parsed.month)
             return (Timestamp(datetime(parsed.year, parsed.month, 1),
                               tz=self.tz),
                     Timestamp(datetime(parsed.year, parsed.month, d, 23,
                                        59, 59, 999999), tz=self.tz))
         elif reso == 'quarter':
             qe = (((parsed.month - 1) + 2) % 12) + 1  # two months ahead
-            d = libts.monthrange(parsed.year, qe)[1]   # at end of month
+            d = ccalendar.get_days_in_month(parsed.year, qe)  # at end of month
             return (Timestamp(datetime(parsed.year, parsed.month, 1),
                               tz=self.tz),
                     Timestamp(datetime(parsed.year, qe, d, 23, 59,

pandas/tests/tseries/offsets/test_offsets.py

@@ -41,12 +41,6 @@
 from .common import assert_offset_equal, assert_onOffset
 
 
-def test_monthrange():
-    import calendar
-    for y in range(2000, 2013):
-        for m in range(1, 13):
-            assert tslib.monthrange(y, m) == calendar.monthrange(y, m)
-
 ####
 # Misc function tests
 ####

pandas/tseries/offsets.py

@@ -1140,7 +1140,7 @@ def apply(self, other):
         # shift `other` to self.day_of_month, incrementing `n` if necessary
         n = liboffsets.roll_convention(other.day, self.n, self.day_of_month)
 
-        days_in_month = tslib.monthrange(other.year, other.month)[1]
+        days_in_month = ccalendar.get_days_in_month(other.year, other.month)
 
         # For SemiMonthBegin on other.day == 1 and
         # SemiMonthEnd on other.day == days_in_month,
@@ -1217,7 +1217,7 @@ class SemiMonthEnd(SemiMonthOffset):
     def onOffset(self, dt):
         if self.normalize and not _is_normalized(dt):
             return False
-        _, days_in_month = tslib.monthrange(dt.year, dt.month)
+        days_in_month = ccalendar.get_days_in_month(dt.year, dt.month)
         return dt.day in (self.day_of_month, days_in_month)
 
     def _apply(self, n, other):

setup.py

@@ -603,6 +603,7 @@ def pxd(name):
         'pyxfile': '_libs/tslibs/resolution',
         'pxdfiles': ['_libs/src/util',
                      '_libs/khash',
+                     '_libs/tslibs/ccalendar',
                      '_libs/tslibs/frequencies',
                      '_libs/tslibs/timezones'],
         'depends': tseries_depends,