standalone implementation of ccalendar (pandas-dev#18540)

pandas/_libs/tslibs/ccalendar.pxd

@@ -0,0 +1,12 @@
+# -*- coding: utf-8 -*-
+# cython: profile=False
+
+from cython cimport Py_ssize_t
+
+from numpy cimport int64_t, int32_t
+
+
+cdef int dayofweek(int y, int m, int m) nogil
+cdef bint is_leapyear(int64_t year) nogil
+cpdef int32_t get_days_in_month(int year, Py_ssize_t month) nogil
+cpdef int32_t get_week_of_year(int year, int month, int day) nogil

pandas/_libs/tslibs/ccalendar.pyx

@@ -0,0 +1,163 @@
+# -*- coding: utf-8 -*-
+# cython: profile=False
+# cython: boundscheck=False
+"""
+Cython implementations of functions resembling the stdlib calendar module
+"""
+
+cimport cython
+from cython cimport Py_ssize_t
+
+import numpy as np
+cimport numpy as np
+from numpy cimport int64_t, int32_t
+np.import_array()
+
+
+# ----------------------------------------------------------------------
+# Constants
+
+# Slightly more performant cython lookups than a 2D table
+# The first 12 entries correspond to month lengths for non-leap years.
+# The remaining 12 entries give month lengths for leap years
+cdef int32_t* days_per_month_array = [
+    31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31,
+    31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]
+
+cdef int* sakamoto_arr = [0, 3, 2, 5, 0, 3, 5, 1, 4, 6, 2, 4]
+
+# The first 13 entries give the month days elapsed as of the first of month N
+# (or the total number of days in the year for N=13) in non-leap years.
+# The remaining 13 entries give the days elapsed in leap years.
+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]
+
+# ----------------------------------------------------------------------
+
+
+@cython.wraparound(False)
+@cython.boundscheck(False)
+cpdef inline int32_t get_days_in_month(int year, Py_ssize_t month) nogil:
+    """Return the number of days in the given month of the given year.
+
+    Parameters
+    ----------
+    year : int
+    month : int
+
+    Returns
+    -------
+    days_in_month : int
+
+    Notes
+    -----
+    Assumes that the arguments are valid.  Passing a month not between 1 and 12
+    risks a segfault.
+    """
+    return days_per_month_array[12 * is_leapyear(year) + month - 1]
+
+
+@cython.wraparound(False)
+@cython.boundscheck(False)
+@cython.cdivision
+cdef int dayofweek(int y, int m, int d) nogil:
+    """Find the day of week for the date described by the Y/M/D triple y, m, d
+    using Sakamoto's method, from wikipedia.
+
+    0 represents Monday.  See [1]_.
+
+    Parameters
+    ----------
+    y : int
+    m : int
+    d : int
+
+    Returns
+    -------
+    weekday : int
+
+    Notes
+    -----
+    Assumes that y, m, d, represents a valid date.
+
+    See Also
+    --------
+    [1] https://docs.python.org/3.6/library/calendar.html#calendar.weekday
+
+    [2] https://en.wikipedia.org/wiki/\
+    Determination_of_the_day_of_the_week#Sakamoto.27s_methods
+    """
+    cdef:
+        int day
+
+    y -= m < 3
+    day = (y + y / 4 - y / 100 + y / 400 + sakamoto_arr[m - 1] + d) % 7
+    # convert to python day
+    return (day + 6) % 7
+
+
+cdef bint is_leapyear(int64_t year) nogil:
+    """Returns 1 if the given year is a leap year, 0 otherwise.
+
+    Parameters
+    ----------
+    year : int
+
+    Returns
+    -------
+    is_leap : bool
+    """
+    return ((year & 0x3) == 0 and  # year % 4 == 0
+            ((year % 100) != 0 or (year % 400) == 0))
+
+
+@cython.wraparound(False)
+@cython.boundscheck(False)
+cpdef int32_t get_week_of_year(int year, int month, int day) nogil:
+    """Return the ordinal week-of-year for the given day.
+
+    Parameters
+    ----------
+    year : int
+    month : int
+    day : int
+
+    Returns
+    -------
+    week_of_year : int32_t
+
+    Notes
+    -----
+    Assumes the inputs describe a valid date.
+    """
+    cdef:
+        bint isleap, isleap_prev
+        int32_t mo_off
+        int32_t doy, dow
+        int woy
+
+    isleap = is_leapyear(year)
+    isleap_prev = is_leapyear(year - 1)
+
+    mo_off = _month_offset[isleap * 13 + month - 1]
+
+    doy = mo_off + day
+    dow = dayofweek(year, month, day)
+
+    # estimate
+    woy = (doy - 1) - dow + 3
+    if woy >= 0:
+        woy = woy / 7 + 1
+
+    # verify
+    if woy < 0:
+        if (woy > -2) or (woy == -2 and isleap_prev):
+            woy = 53
+        else:
+            woy = 52
+    elif woy == 53:
+        if 31 - day + dow < 3:
+            woy = 1
+
+    return woy

pandas/_libs/tslibs/fields.pyx

@@ -17,9 +17,10 @@ from numpy cimport ndarray, int64_t, int32_t, int8_t
 np.import_array()
 
 
+from ccalendar cimport (get_days_in_month, is_leapyear, dayofweek,
+                        get_week_of_year)
 from np_datetime cimport (pandas_datetimestruct, pandas_timedeltastruct,
-                          dt64_to_dtstruct, td64_to_tdstruct,
-                          days_per_month_table, is_leapyear, dayofweek)
+                          dt64_to_dtstruct, td64_to_tdstruct)
 from nattype cimport NPY_NAT
 
 
@@ -379,7 +380,7 @@ def get_date_field(ndarray[int64_t] dtindex, object field):
         ndarray[int32_t, ndim=2] _month_offset
         int isleap, isleap_prev
         pandas_datetimestruct dts
-        int mo_off, doy, dow, woy
+        int mo_off, doy, dow
 
     _month_offset = np.array(
         [[ 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 365 ],
@@ -507,28 +508,7 @@ def get_date_field(ndarray[int64_t] dtindex, object field):
                     continue
 
                 dt64_to_dtstruct(dtindex[i], &dts)
-                isleap = is_leapyear(dts.year)
-                isleap_prev = is_leapyear(dts.year - 1)
-                mo_off = _month_offset[isleap, dts.month - 1]
-                doy = mo_off + dts.day
-                dow = dayofweek(dts.year, dts.month, dts.day)
-
-                # estimate
-                woy = (doy - 1) - dow + 3
-                if woy >= 0:
-                    woy = woy / 7 + 1
-
-                # verify
-                if woy < 0:
-                    if (woy > -2) or (woy == -2 and isleap_prev):
-                        woy = 53
-                    else:
-                        woy = 52
-                elif woy == 53:
-                    if 31 - dts.day + dow < 3:
-                        woy = 1
-
-                out[i] = woy
+                out[i] = get_week_of_year(dts.year, dts.month, dts.day)
         return out
 
     elif field == 'q':
@@ -551,7 +531,7 @@ def get_date_field(ndarray[int64_t] dtindex, object field):
                     continue
 
                 dt64_to_dtstruct(dtindex[i], &dts)
-                out[i] = days_in_month(dts)
+                out[i] = get_days_in_month(dts.year, dts.month)
         return out
     elif field == 'is_leap_year':
         return isleapyear_arr(get_date_field(dtindex, 'Y'))
@@ -676,10 +656,6 @@ def get_timedelta_field(ndarray[int64_t] tdindex, object field):
     raise ValueError("Field %s not supported" % field)
 
 
-cdef inline int days_in_month(pandas_datetimestruct dts) nogil:
-    return days_per_month_table[is_leapyear(dts.year)][dts.month - 1]
-
-
 cpdef isleapyear_arr(ndarray years):
     """vectorized version of isleapyear; NaT evaluates as False"""
     cdef:

pandas/_libs/tslibs/timestamps.pyx

@@ -20,6 +20,7 @@ from util cimport (is_datetime64_object, is_timedelta64_object,
                    is_integer_object, is_string_object,
                    INT64_MAX)
 
+cimport ccalendar
 from conversion import tz_localize_to_utc, date_normalize
 from conversion cimport (tz_convert_single, _TSObject,
                          convert_to_tsobject, convert_datetime_to_tsobject)
@@ -699,6 +700,9 @@ class Timestamp(_Timestamp):
 
     @property
     def week(self):
+        if self.freq is None:
+            # fastpath for non-business
+            return ccalendar.get_week_of_year(self.year, self.month, self.day)
         return self._get_field('woy')
 
     weekofyear = week
@@ -709,7 +713,7 @@ class Timestamp(_Timestamp):
 
     @property
     def days_in_month(self):
-        return self._get_field('dim')
+        return ccalendar.get_days_in_month(self.year, self.month)
 
     daysinmonth = days_in_month
 

setup.py

@@ -317,6 +317,7 @@ class CheckSDist(sdist_class):
                  'pandas/_libs/skiplist.pyx',
                  'pandas/_libs/sparse.pyx',
                  'pandas/_libs/parsers.pyx',
+                 'pandas/_libs/tslibs/ccalendar.pyx',
                  'pandas/_libs/tslibs/period.pyx',
                  'pandas/_libs/tslibs/strptime.pyx',
                  'pandas/_libs/tslibs/np_datetime.pyx',
@@ -537,6 +538,8 @@ def pxd(name):
                      '_libs/tslibs/nattype'],
         'depends': tseries_depends,
         'sources': np_datetime_sources},
+    '_libs.tslibs.ccalendar': {
+        'pyxfile': '_libs/tslibs/ccalendar'},
     '_libs.tslibs.conversion': {
         'pyxfile': '_libs/tslibs/conversion',
         'pxdfiles': ['_libs/src/util',
@@ -547,7 +550,8 @@ def pxd(name):
         'sources': np_datetime_sources},
     '_libs.tslibs.fields': {
         'pyxfile': '_libs/tslibs/fields',
-        'pxdfiles': ['_libs/tslibs/nattype'],
+        'pxdfiles': ['_libs/tslibs/ccalendar',
+                     '_libs/tslibs/nattype'],
         'depends': tseries_depends,
         'sources': np_datetime_sources},
     '_libs.tslibs.frequencies': {
@@ -594,6 +598,7 @@ def pxd(name):
     '_libs.tslibs.timestamps': {
         'pyxfile': '_libs/tslibs/timestamps',
         'pxdfiles': ['_libs/src/util',
+                     '_libs/tslibs/ccalendar',
                      '_libs/tslibs/conversion',
                      '_libs/tslibs/nattype',
                      '_libs/tslibs/timedeltas',