REF: ensure we have offset objects in plotting functions (#34585)

Author: jbrockmendel

pandas/plotting/_matplotlib/converter.py

@@ -11,7 +11,9 @@
 import numpy as np
 
 from pandas._libs import lib, tslibs
-from pandas._libs.tslibs.frequencies import FreqGroup, get_freq_code, get_freq_group
+from pandas._libs.tslibs import to_offset
+from pandas._libs.tslibs.frequencies import FreqGroup, get_freq_group
+from pandas._libs.tslibs.offsets import BaseOffset
 
 from pandas.core.dtypes.common import (
     is_datetime64_ns_dtype,
@@ -522,34 +524,36 @@ def has_level_label(label_flags, vmin):
         return True
 
 
-def _daily_finder(vmin, vmax, freq):
+def _daily_finder(vmin, vmax, freq: BaseOffset):
+    dtype_code = freq._period_dtype_code
+
     periodsperday = -1
 
-    if freq >= FreqGroup.FR_HR:
-        if freq == FreqGroup.FR_NS:
+    if dtype_code >= FreqGroup.FR_HR:
+        if dtype_code == FreqGroup.FR_NS:
             periodsperday = 24 * 60 * 60 * 1000000000
-        elif freq == FreqGroup.FR_US:
+        elif dtype_code == FreqGroup.FR_US:
             periodsperday = 24 * 60 * 60 * 1000000
-        elif freq == FreqGroup.FR_MS:
+        elif dtype_code == FreqGroup.FR_MS:
             periodsperday = 24 * 60 * 60 * 1000
-        elif freq == FreqGroup.FR_SEC:
+        elif dtype_code == FreqGroup.FR_SEC:
             periodsperday = 24 * 60 * 60
-        elif freq == FreqGroup.FR_MIN:
+        elif dtype_code == FreqGroup.FR_MIN:
             periodsperday = 24 * 60
-        elif freq == FreqGroup.FR_HR:
+        elif dtype_code == FreqGroup.FR_HR:
             periodsperday = 24
         else:  # pragma: no cover
-            raise ValueError(f"unexpected frequency: {freq}")
+            raise ValueError(f"unexpected frequency: {dtype_code}")
         periodsperyear = 365 * periodsperday
         periodspermonth = 28 * periodsperday
 
-    elif freq == FreqGroup.FR_BUS:
+    elif dtype_code == FreqGroup.FR_BUS:
         periodsperyear = 261
         periodspermonth = 19
-    elif freq == FreqGroup.FR_DAY:
+    elif dtype_code == FreqGroup.FR_DAY:
         periodsperyear = 365
         periodspermonth = 28
-    elif get_freq_group(freq) == FreqGroup.FR_WK:
+    elif get_freq_group(dtype_code) == FreqGroup.FR_WK:
         periodsperyear = 52
         periodspermonth = 3
     else:  # pragma: no cover
@@ -676,7 +680,7 @@ def _second_finder(label_interval):
     elif span <= periodsperyear // 4:
         month_start = period_break(dates_, "month")
         info_maj[month_start] = True
-        if freq < FreqGroup.FR_HR:
+        if dtype_code < FreqGroup.FR_HR:
             info["min"] = True
         else:
             day_start = period_break(dates_, "day")
@@ -884,21 +888,20 @@ def _annual_finder(vmin, vmax, freq):
     return info
 
 
-def get_finder(freq):
-    if isinstance(freq, str):
-        freq = get_freq_code(freq)[0]
-    fgroup = get_freq_group(freq)
+def get_finder(freq: BaseOffset):
+    dtype_code = freq._period_dtype_code
+    fgroup = (dtype_code // 1000) * 1000
 
     if fgroup == FreqGroup.FR_ANN:
         return _annual_finder
     elif fgroup == FreqGroup.FR_QTR:
         return _quarterly_finder
-    elif freq == FreqGroup.FR_MTH:
+    elif dtype_code == FreqGroup.FR_MTH:
         return _monthly_finder
-    elif (freq >= FreqGroup.FR_BUS) or fgroup == FreqGroup.FR_WK:
+    elif (dtype_code >= FreqGroup.FR_BUS) or fgroup == FreqGroup.FR_WK:
         return _daily_finder
     else:  # pragma: no cover
-        raise NotImplementedError(f"Unsupported frequency: {freq}")
+        raise NotImplementedError(f"Unsupported frequency: {dtype_code}")
 
 
 class TimeSeries_DateLocator(Locator):
@@ -930,8 +933,7 @@ def __init__(
         day=1,
         plot_obj=None,
     ):
-        if isinstance(freq, str):
-            freq = get_freq_code(freq)[0]
+        freq = to_offset(freq)
         self.freq = freq
         self.base = base
         (self.quarter, self.month, self.day) = (quarter, month, day)
@@ -1009,8 +1011,7 @@ class TimeSeries_DateFormatter(Formatter):
     """
 
     def __init__(self, freq, minor_locator=False, dynamic_mode=True, plot_obj=None):
-        if isinstance(freq, str):
-            freq = get_freq_code(freq)[0]
+        freq = to_offset(freq)
         self.format = None
         self.freq = freq
         self.locs = []

pandas/tests/plotting/test_datetimelike.py

@@ -6,6 +6,7 @@
 import numpy as np
 import pytest
 
+from pandas._libs.tslibs import to_offset
 import pandas.util._test_decorators as td
 
 from pandas import DataFrame, Index, NaT, Series, isna
@@ -397,12 +398,12 @@ def _test(ax):
     def test_get_finder(self):
         import pandas.plotting._matplotlib.converter as conv
 
-        assert conv.get_finder("B") == conv._daily_finder
-        assert conv.get_finder("D") == conv._daily_finder
-        assert conv.get_finder("M") == conv._monthly_finder
-        assert conv.get_finder("Q") == conv._quarterly_finder
-        assert conv.get_finder("A") == conv._annual_finder
-        assert conv.get_finder("W") == conv._daily_finder
+        assert conv.get_finder(to_offset("B")) == conv._daily_finder
+        assert conv.get_finder(to_offset("D")) == conv._daily_finder
+        assert conv.get_finder(to_offset("M")) == conv._monthly_finder
+        assert conv.get_finder(to_offset("Q")) == conv._quarterly_finder
+        assert conv.get_finder(to_offset("A")) == conv._annual_finder
+        assert conv.get_finder(to_offset("W")) == conv._daily_finder
 
     @pytest.mark.slow
     def test_finder_daily(self):