BUG/CLN - offsets.Day(n>2) not properly anchoring dates, and make cod…

…e more readable

pandas/core/resample.py

@@ -1546,30 +1546,24 @@ def _get_period_bins(self, ax):
         end = ax.max().asfreq(self.freq, how='end')
         offset = 0
 
+        # GH 23882
         if self.base:
-            start = start.to_timestamp()
-            end = end.to_timestamp()
-
             # get base adjusted bin edge labels
-            p_start, p_end = _get_range_edges(start,
-                                              end,
-                                              self.freq,
-                                              closed=self.closed,
-                                              base=self.base,
-                                              compensate_edges=True)
-
-            labels = binner = PeriodIndex(start=p_start, end=p_end,
-                                          freq=self.freq,
-                                          name=ax.name)
+            p_start, end = _get_range_edges(start,
+                                            end,
+                                            self.freq,
+                                            closed=self.closed,
+                                            base=self.base)
 
             # Get offset for bin edge (not label edge) adjustment
             start_offset = (pd.Period(start, self.freq)
                             - pd.Period(p_start, self.freq))
             # remove /freq_mult once period diff scaling bug is fixed
             offset = int(start_offset.n / freq_mult) % freq_mult
-        else:
-            labels = binner = PeriodIndex(start=start, end=end,
-                                          freq=self.freq, name=ax.name)
+            start = p_start
+
+        labels = binner = PeriodIndex(start=start, end=end,
+                                      freq=self.freq, name=ax.name)
 
         i8 = memb.asi8
 
@@ -1608,18 +1602,27 @@ def _take_new_index(obj, indexer, new_index, axis=0):
         raise ValueError("'obj' should be either a Series or a DataFrame")
 
 
-def _get_range_edges(first, last, offset, closed='left', base=0,
-                     compensate_edges=False):
-    first_ = first
-    last_ = last
+def _get_range_edges(first, last, offset, closed='left', base=0):
+    if type(first) != type(last):
+        raise TypeError("'first' and 'last' must be same type")
+
+    # make proper adjustments for Periods #GH 23882
+    is_period = False
+    adjust_first = adjust_last = False
+    if isinstance(first, pd.Period):
+        is_period = True
+        first = first.to_timestamp()
+        last = last.to_timestamp()
+        adjust_first = not offset.onOffset(first)
+        adjust_last = offset.onOffset(last)
 
     additional_adjust = True
     if isinstance(offset, Tick):
         is_day = isinstance(offset, Day)
         day_nanos = delta_to_nanoseconds(timedelta(1))
 
-        # #1165
-        if (is_day and day_nanos % offset.nanos == 0) or not is_day:
+        # #1165 / #24127
+        if (is_day and not offset.nanos % day_nanos) or not is_day:
             additional_adjust = False
             # Don't return immediately because might need to compensate edges
             first, last = _adjust_dates_anchored(first, last, offset,
@@ -1637,27 +1640,9 @@ def _get_range_edges(first, last, offset, closed='left', base=0,
 
         last = Timestamp(last + offset)
 
-    if compensate_edges:
-        first, last = _compensate_edges(first, last, first_, last_, offset)
-
-    return first, last
-
-
-def _compensate_edges(adj_first, adj_last, orig_first, orig_last, offset):
-    # Implement this function in expanded form, instead of the shorter form
-    # to ensure that all these cases are covered in code coverage reports
-
-    # first = adj_first + offset * (not offset.onOffset(orig_first))
-    if not offset.onOffset(orig_first):
-        first = adj_first + offset
-    else:
-        first = adj_first
-
-    # last = adj_last - offset * offset.onOffset(orig_last)
-    if offset.onOffset(orig_last):
-        last = adj_last - offset
-    else:
-        last = adj_last
+    if is_period:
+        first = (first + adjust_first * offset).to_period(offset)
+        last = (last - adjust_last * offset).to_period(offset)
 
     return first, last