implement shift_quarters --> apply_index for quarters and years (#18522)

pandas/_libs/tslibs/offsets.pyx

@@ -17,8 +17,6 @@ np.import_array()
 
 from util cimport is_string_object, is_integer_object
 
-from pandas._libs.tslib import monthrange
-
 from conversion cimport tz_convert_single, pydt_to_i8
 from frequencies cimport get_freq_code
 from nattype cimport NPY_NAT
@@ -471,6 +469,160 @@ cdef inline int month_add_months(pandas_datetimestruct dts, int months) nogil:
     return 12 if new_month == 0 else new_month
 
 
+@cython.wraparound(False)
+@cython.boundscheck(False)
+def shift_quarters(int64_t[:] dtindex, int quarters,
+                   int q1start_month, object day, int modby=3):
+    """
+    Given an int64 array representing nanosecond timestamps, shift all elements
+    by the specified number of quarters using DateOffset semantics.
+
+    Parameters
+    ----------
+    dtindex : int64_t[:] timestamps for input dates
+    quarters : int number of quarters to shift
+    q1start_month : int month in which Q1 begins by convention
+    day : {'start', 'end', 'business_start', 'business_end'}
+    modby : int (3 for quarters, 12 for years)
+
+    Returns
+    -------
+    out : ndarray[int64_t]
+    """
+    cdef:
+        Py_ssize_t i
+        pandas_datetimestruct dts
+        int count = len(dtindex)
+        int months_to_roll, months_since, n, compare_day
+        bint roll_check
+        int64_t[:] out = np.empty(count, dtype='int64')
+
+    if day == 'start':
+        with nogil:
+            for i in range(count):
+                if dtindex[i] == NPY_NAT:
+                    out[i] = NPY_NAT
+                    continue
+
+                dt64_to_dtstruct(dtindex[i], &dts)
+                n = quarters
+
+                months_since = (dts.month - q1start_month) % modby
+
+                # offset semantics - if on the anchor point and going backwards
+                # shift to next
+                if n <= 0 and (months_since != 0 or
+                               (months_since == 0 and dts.day > 1)):
+                    n += 1
+
+                dts.year = year_add_months(dts, modby * n - months_since)
+                dts.month = month_add_months(dts, modby * n - months_since)
+                dts.day = 1
+
+                out[i] = dtstruct_to_dt64(&dts)
+
+    elif day == 'end':
+        with nogil:
+            for i in range(count):
+                if dtindex[i] == NPY_NAT:
+                    out[i] = NPY_NAT
+                    continue
+
+                dt64_to_dtstruct(dtindex[i], &dts)
+                n = quarters
+
+                months_since = (dts.month - q1start_month) % modby
+
+                if n <= 0 and months_since != 0:
+                    # The general case of this condition would be
+                    # `months_since != 0 or (months_since == 0 and
+                    #    dts.day > get_days_in_month(dts.year, dts.month))`
+                    # but the get_days_in_month inequality would never hold.
+                    n += 1
+                elif n > 0 and (months_since == 0 and
+                                dts.day < get_days_in_month(dts.year,
+                                                            dts.month)):
+                    n -= 1
+
+                dts.year = year_add_months(dts, modby * n - months_since)
+                dts.month = month_add_months(dts, modby * n - months_since)
+                dts.day = get_days_in_month(dts.year, dts.month)
+
+                out[i] = dtstruct_to_dt64(&dts)
+
+    elif day == 'business_start':
+        with nogil:
+            for i in range(count):
+                if dtindex[i] == NPY_NAT:
+                    out[i] = NPY_NAT
+                    continue
+
+                dt64_to_dtstruct(dtindex[i], &dts)
+                n = quarters
+
+                months_since = (dts.month - q1start_month) % modby
+                compare_month = dts.month - months_since
+                compare_month = compare_month or 12
+                # compare_day is only relevant for comparison in the case
+                # where months_since == 0.
+                compare_day = get_firstbday(dts.year, compare_month)
+
+                if n <= 0 and (months_since != 0 or
+                               (months_since == 0 and dts.day > compare_day)):
+                    # make sure to roll forward, so negate
+                    n += 1
+                elif n > 0 and (months_since == 0 and dts.day < compare_day):
+                    # pretend to roll back if on same month but
+                    # before compare_day
+                    n -= 1
+
+                dts.year = year_add_months(dts, modby * n - months_since)
+                dts.month = month_add_months(dts, modby * n - months_since)
+
+                dts.day = get_firstbday(dts.year, dts.month)
+
+                out[i] = dtstruct_to_dt64(&dts)
+
+    elif day == 'business_end':
+        with nogil:
+            for i in range(count):
+                if dtindex[i] == NPY_NAT:
+                    out[i] = NPY_NAT
+                    continue
+
+                dt64_to_dtstruct(dtindex[i], &dts)
+                n = quarters
+
+                months_since = (dts.month - q1start_month) % modby
+                compare_month = dts.month - months_since
+                compare_month = compare_month or 12
+                # compare_day is only relevant for comparison in the case
+                # where months_since == 0.
+                compare_day = get_lastbday(dts.year, compare_month)
+
+                if n <= 0 and (months_since != 0 or
+                               (months_since == 0 and dts.day > compare_day)):
+                    # make sure to roll forward, so negate
+                    n += 1
+                elif n > 0 and (months_since == 0 and dts.day < compare_day):
+                    # pretend to roll back if on same month but
+                    # before compare_day
+                    n -= 1
+
+                dts.year = year_add_months(dts, modby * n - months_since)
+                dts.month = month_add_months(dts, modby * n - months_since)
+
+                dts.day = get_lastbday(dts.year, dts.month)
+
+                out[i] = dtstruct_to_dt64(&dts)
+
+    else:
+        raise ValueError("day must be None, 'start', 'end', "
+                         "'business_start', or 'business_end'")
+
+    return np.asarray(out)
+
+
 @cython.wraparound(False)
 @cython.boundscheck(False)
 def shift_months(int64_t[:] dtindex, int months, object day=None):

pandas/tests/tseries/offsets/test_yqm_offsets.py

@@ -33,9 +33,15 @@ def test_quarterly_dont_normalize():
         assert (result.time() == date.time())
 
 
-@pytest.mark.parametrize('offset', [MonthBegin(), MonthEnd(),
-                                    BMonthBegin(), BMonthEnd()])
-def test_apply_index(offset):
+@pytest.mark.parametrize('n', [-2, 1])
+@pytest.mark.parametrize('cls', [MonthBegin, MonthEnd,
+                                 BMonthBegin, BMonthEnd,
+                                 QuarterBegin, QuarterEnd,
+                                 BQuarterBegin, BQuarterEnd,
+                                 YearBegin, YearEnd,
+                                 BYearBegin, BYearEnd])
+def test_apply_index(cls, n):
+    offset = cls(n=n)
     rng = pd.date_range(start='1/1/2000', periods=100000, freq='T')
     ser = pd.Series(rng)
 

pandas/tseries/offsets.py

@@ -27,7 +27,7 @@
     apply_index_wraps,
     roll_yearday,
     shift_month,
-    BeginMixin, EndMixin,
+    EndMixin,
     BaseOffset)
 
 
@@ -1028,10 +1028,7 @@ def cbday(self):
 
     @cache_readonly
     def m_offset(self):
-        kwds = self.kwds
-        kwds = {key: kwds[key] for key in kwds
-                if key not in ['calendar', 'weekmask', 'holidays', 'offset']}
-        return MonthEnd(n=1, normalize=self.normalize, **kwds)
+        return MonthEnd(n=1, normalize=self.normalize)
 
     @apply_wraps
     def apply(self, other):
@@ -1106,10 +1103,7 @@ def cbday(self):
 
     @cache_readonly
     def m_offset(self):
-        kwds = self.kwds
-        kwds = {key: kwds[key] for key in kwds
-                if key not in ['calendar', 'weekmask', 'holidays', 'offset']}
-        return MonthBegin(n=1, normalize=self.normalize, **kwds)
+        return MonthBegin(n=1, normalize=self.normalize)
 
     @apply_wraps
     def apply(self, other):
@@ -1254,12 +1248,9 @@ def onOffset(self, dt):
 
     def _apply(self, n, other):
         # if other.day is not day_of_month move to day_of_month and update n
-        if other.day < self.day_of_month:
-            other = other.replace(day=self.day_of_month)
-            if n > 0:
-                n -= 1
+        if n > 0 and other.day < self.day_of_month:
+            n -= 1
         elif other.day > self.day_of_month:
-            other = other.replace(day=self.day_of_month)
             n += 1
 
         months = n // 2
@@ -1309,12 +1300,9 @@ def onOffset(self, dt):
     def _apply(self, n, other):
         # if other.day is not day_of_month move to day_of_month and update n
         if other.day < self.day_of_month:
-            other = other.replace(day=self.day_of_month)
             n -= 1
-        elif other.day > self.day_of_month:
-            other = other.replace(day=self.day_of_month)
-            if n <= 0:
-                n += 1
+        elif n <= 0 and other.day > self.day_of_month:
+            n += 1
 
         months = n // 2 + n % 2
         day = 1 if n % 2 else self.day_of_month
@@ -1471,6 +1459,7 @@ def apply(self, other):
     def getOffsetOfMonth(self, dt):
         w = Week(weekday=self.weekday)
         d = datetime(dt.year, dt.month, 1, tzinfo=dt.tzinfo)
+        # TODO: Is this DST-safe?
         d = w.rollforward(d)
         return d + timedelta(weeks=self.week)
 
@@ -1550,6 +1539,7 @@ def getOffsetOfMonth(self, dt):
         d = datetime(dt.year, dt.month, 1, dt.hour, dt.minute,
                      dt.second, dt.microsecond, tzinfo=dt.tzinfo)
         eom = m.rollforward(d)
+        # TODO: Is this DST-safe?
         w = Week(weekday=self.weekday)
         return w.rollback(eom)
 
@@ -1635,6 +1625,12 @@ def onOffset(self, dt):
         modMonth = (dt.month - self.startingMonth) % 3
         return modMonth == 0 and dt.day == self._get_offset_day(dt)
 
+    @apply_index_wraps
+    def apply_index(self, dtindex):
+        shifted = liboffsets.shift_quarters(dtindex.asi8, self.n,
+                                            self.startingMonth, self._day_opt)
+        return dtindex._shallow_copy(shifted)
+
 
 class BQuarterEnd(QuarterOffset):
     """DateOffset increments between business Quarter dates
@@ -1659,7 +1655,7 @@ class BQuarterBegin(QuarterOffset):
     _day_opt = 'business_start'
 
 
-class QuarterEnd(EndMixin, QuarterOffset):
+class QuarterEnd(QuarterOffset):
     """DateOffset increments between business Quarter dates
     startingMonth = 1 corresponds to dates like 1/31/2007, 4/30/2007, ...
     startingMonth = 2 corresponds to dates like 2/28/2007, 5/31/2007, ...
@@ -1670,25 +1666,14 @@ class QuarterEnd(EndMixin, QuarterOffset):
     _prefix = 'Q'
     _day_opt = 'end'
 
-    @apply_index_wraps
-    def apply_index(self, i):
-        return self._end_apply_index(i, self.freqstr)
-
 
-class QuarterBegin(BeginMixin, QuarterOffset):
+class QuarterBegin(QuarterOffset):
     _outputName = 'QuarterBegin'
     _default_startingMonth = 3
     _from_name_startingMonth = 1
     _prefix = 'QS'
     _day_opt = 'start'
 
-    @apply_index_wraps
-    def apply_index(self, i):
-        freq_month = 12 if self.startingMonth == 1 else self.startingMonth - 1
-        month = liboffsets._int_to_month[freq_month]
-        freqstr = 'Q-{month}'.format(month=month)
-        return self._beg_apply_index(i, freqstr)
-
 
 # ---------------------------------------------------------------------
 # Year-Based Offset Classes
@@ -1709,6 +1694,13 @@ def apply(self, other):
         months = years * 12 + (self.month - other.month)
         return shift_month(other, months, self._day_opt)
 
+    @apply_index_wraps
+    def apply_index(self, dtindex):
+        shifted = liboffsets.shift_quarters(dtindex.asi8, self.n,
+                                            self.month, self._day_opt,
+                                            modby=12)
+        return dtindex._shallow_copy(shifted)
+
     def onOffset(self, dt):
         if self.normalize and not _is_normalized(dt):
             return False
@@ -1752,31 +1744,19 @@ class BYearBegin(YearOffset):
     _day_opt = 'business_start'
 
 
-class YearEnd(EndMixin, YearOffset):
+class YearEnd(YearOffset):
     """DateOffset increments between calendar year ends"""
     _default_month = 12
     _prefix = 'A'
     _day_opt = 'end'
 
-    @apply_index_wraps
-    def apply_index(self, i):
-        # convert month anchor to annual period tuple
-        return self._end_apply_index(i, self.freqstr)
 
-
-class YearBegin(BeginMixin, YearOffset):
+class YearBegin(YearOffset):
     """DateOffset increments between calendar year begin dates"""
     _default_month = 1
     _prefix = 'AS'
     _day_opt = 'start'
 
-    @apply_index_wraps
-    def apply_index(self, i):
-        freq_month = 12 if self.month == 1 else self.month - 1
-        month = liboffsets._int_to_month[freq_month]
-        freqstr = 'A-{month}'.format(month=month)
-        return self._beg_apply_index(i, freqstr)
-
 
 # ---------------------------------------------------------------------
 # Special Offset Classes
@@ -2245,7 +2225,8 @@ def __eq__(self, other):
         if isinstance(other, Tick):
             return self.delta == other.delta
         else:
-            return DateOffset.__eq__(self, other)
+            # TODO: Are there cases where this should raise TypeError?
+            return False
 
     # This is identical to DateOffset.__hash__, but has to be redefined here
     # for Python 3, because we've redefined __eq__.
@@ -2261,7 +2242,8 @@ def __ne__(self, other):
         if isinstance(other, Tick):
             return self.delta != other.delta
         else:
-            return DateOffset.__ne__(self, other)
+            # TODO: Are there cases where this should raise TypeError?
+            return True
 
     @property
     def delta(self):