REF: move generate_range from offsets to the one place it is used (#34146)

Author: jbrockmendel

pandas/core/arrays/datetimes.py

@@ -48,7 +48,7 @@
 import pandas.core.common as com
 
 from pandas.tseries.frequencies import get_period_alias, to_offset
-from pandas.tseries.offsets import Day, Tick, generate_range
+from pandas.tseries.offsets import BDay, Day, Tick
 
 _midnight = time(0, 0)
 
@@ -2336,3 +2336,81 @@ def _maybe_localize_point(ts, is_none, is_not_none, freq, tz, ambiguous, nonexis
             localize_args["tz"] = tz
         ts = ts.tz_localize(**localize_args)
     return ts
+
+
+def generate_range(start=None, end=None, periods=None, offset=BDay()):
+    """
+    Generates a sequence of dates corresponding to the specified time
+    offset. Similar to dateutil.rrule except uses pandas DateOffset
+    objects to represent time increments.
+
+    Parameters
+    ----------
+    start : datetime, (default None)
+    end : datetime, (default None)
+    periods : int, (default None)
+    offset : DateOffset, (default BDay())
+
+    Notes
+    -----
+    * This method is faster for generating weekdays than dateutil.rrule
+    * At least two of (start, end, periods) must be specified.
+    * If both start and end are specified, the returned dates will
+    satisfy start <= date <= end.
+
+    Returns
+    -------
+    dates : generator object
+    """
+    offset = to_offset(offset)
+
+    start = Timestamp(start)
+    start = start if start is not NaT else None
+    end = Timestamp(end)
+    end = end if end is not NaT else None
+
+    if start and not offset.is_on_offset(start):
+        start = offset.rollforward(start)
+
+    elif end and not offset.is_on_offset(end):
+        end = offset.rollback(end)
+
+    if periods is None and end < start and offset.n >= 0:
+        end = None
+        periods = 0
+
+    if end is None:
+        end = start + (periods - 1) * offset
+
+    if start is None:
+        start = end - (periods - 1) * offset
+
+    cur = start
+    if offset.n >= 0:
+        while cur <= end:
+            yield cur
+
+            if cur == end:
+                # GH#24252 avoid overflows by not performing the addition
+                # in offset.apply unless we have to
+                break
+
+            # faster than cur + offset
+            next_date = offset.apply(cur)
+            if next_date <= cur:
+                raise ValueError(f"Offset {offset} did not increment date")
+            cur = next_date
+    else:
+        while cur >= end:
+            yield cur
+
+            if cur == end:
+                # GH#24252 avoid overflows by not performing the addition
+                # in offset.apply unless we have to
+                break
+
+            # faster than cur + offset
+            next_date = offset.apply(cur)
+            if next_date >= cur:
+                raise ValueError(f"Offset {offset} did not decrement date")
+            cur = next_date

pandas/tests/indexes/datetimes/test_date_range.py

@@ -16,15 +16,9 @@
 import pandas as pd
 from pandas import DatetimeIndex, Timestamp, bdate_range, date_range, offsets
 import pandas._testing as tm
+from pandas.core.arrays.datetimes import generate_range
 
-from pandas.tseries.offsets import (
-    BDay,
-    CDay,
-    DateOffset,
-    MonthEnd,
-    generate_range,
-    prefix_mapping,
-)
+from pandas.tseries.offsets import BDay, CDay, DateOffset, MonthEnd, prefix_mapping
 
 START, END = datetime(2009, 1, 1), datetime(2010, 1, 1)
 

pandas/tseries/offsets.py

@@ -6,7 +6,6 @@
 import numpy as np
 
 from pandas._libs.tslibs import (
-    NaT,
     Period,
     Timedelta,
     Timestamp,
@@ -2305,89 +2304,6 @@ class Nano(Tick):
 CBMonthBegin = CustomBusinessMonthBegin
 CDay = CustomBusinessDay
 
-# ---------------------------------------------------------------------
-
-
-def generate_range(start=None, end=None, periods=None, offset=BDay()):
-    """
-    Generates a sequence of dates corresponding to the specified time
-    offset. Similar to dateutil.rrule except uses pandas DateOffset
-    objects to represent time increments.
-
-    Parameters
-    ----------
-    start : datetime, (default None)
-    end : datetime, (default None)
-    periods : int, (default None)
-    offset : DateOffset, (default BDay())
-
-    Notes
-    -----
-    * This method is faster for generating weekdays than dateutil.rrule
-    * At least two of (start, end, periods) must be specified.
-    * If both start and end are specified, the returned dates will
-    satisfy start <= date <= end.
-
-    Returns
-    -------
-    dates : generator object
-    """
-    from pandas.tseries.frequencies import to_offset
-
-    offset = to_offset(offset)
-
-    start = Timestamp(start)
-    start = start if start is not NaT else None
-    end = Timestamp(end)
-    end = end if end is not NaT else None
-
-    if start and not offset.is_on_offset(start):
-        start = offset.rollforward(start)
-
-    elif end and not offset.is_on_offset(end):
-        end = offset.rollback(end)
-
-    if periods is None and end < start and offset.n >= 0:
-        end = None
-        periods = 0
-
-    if end is None:
-        end = start + (periods - 1) * offset
-
-    if start is None:
-        start = end - (periods - 1) * offset
-
-    cur = start
-    if offset.n >= 0:
-        while cur <= end:
-            yield cur
-
-            if cur == end:
-                # GH#24252 avoid overflows by not performing the addition
-                # in offset.apply unless we have to
-                break
-
-            # faster than cur + offset
-            next_date = offset.apply(cur)
-            if next_date <= cur:
-                raise ValueError(f"Offset {offset} did not increment date")
-            cur = next_date
-    else:
-        while cur >= end:
-            yield cur
-
-            if cur == end:
-                # GH#24252 avoid overflows by not performing the addition
-                # in offset.apply unless we have to
-                break
-
-            # faster than cur + offset
-            next_date = offset.apply(cur)
-            if next_date >= cur:
-                raise ValueError(f"Offset {offset} did not decrement date")
-            cur = next_date
-
-
 prefix_mapping = {
     offset._prefix: offset
     for offset in [