remove is_period and fix some tests [skip ci]

Author: natmokval

Diff for: pandas/_libs/tslibs/period.pyx

@@ -2372,7 +2372,7 @@ cdef class _Period(PeriodMixin):
         """
         Return a string representation of the frequency.
         """
-        return self.freq.freqstr.replace("ME", "M")
+        return self.freq.freqstr
 
     def __repr__(self) -> str:
         base = self._dtype._dtype_code

Diff for: pandas/conftest.py

@@ -919,7 +919,7 @@ def rand_series_with_duplicate_datetimeindex() -> Series:
     params=[
         (Interval(left=0, right=5), IntervalDtype("int64", "right")),
         (Interval(left=0.1, right=0.5), IntervalDtype("float64", "right")),
-        (Period("2012-01", freq="M"), "period[M]"),
+        (Period("2012-01", freq="ME"), "period[ME]"),
         (Period("2012-02-01", freq="D"), "period[D]"),
         (
             Timestamp("2011-01-01", tz="US/Eastern"),

Diff for: pandas/tests/apply/test_frame_apply.py

@@ -653,8 +653,8 @@ def test_applymap_box():
             ],
             "c": [pd.Timedelta("1 days"), pd.Timedelta("2 days")],
             "d": [
-                pd.Period("2011-01-01", freq="M"),
-                pd.Period("2011-01-02", freq="M"),
+                pd.Period("2011-01-01", freq="ME"),
+                pd.Period("2011-01-02", freq="ME"),
             ],
         }
     )

Diff for: pandas/tests/apply/test_series_apply.py

@@ -182,11 +182,11 @@ def test_apply_box():
     tm.assert_series_equal(res, exp)
 
     # period
-    vals = [pd.Period("2011-01-01", freq="M"), pd.Period("2011-01-02", freq="M")]
+    vals = [pd.Period("2011-01-01", freq="ME"), pd.Period("2011-01-02", freq="ME")]
     s = Series(vals)
-    assert s.dtype == "Period[M]"
+    assert s.dtype == "Period[ME]"
     res = s.apply(lambda x: f"{type(x).__name__}_{x.freqstr}")
-    exp = Series(["Period_M", "Period_M"])
+    exp = Series(["Period_ME", "Period_ME"])
     tm.assert_series_equal(res, exp)
 
 
@@ -740,11 +740,11 @@ def test_map_box():
     tm.assert_series_equal(res, exp)
 
     # period
-    vals = [pd.Period("2011-01-01", freq="M"), pd.Period("2011-01-02", freq="M")]
+    vals = [pd.Period("2011-01-01", freq="ME"), pd.Period("2011-01-02", freq="ME")]
     s = Series(vals)
-    assert s.dtype == "Period[M]"
+    assert s.dtype == "Period[ME]"
     res = s.apply(lambda x: f"{type(x).__name__}_{x.freqstr}")
-    exp = Series(["Period_M", "Period_M"])
+    exp = Series(["Period_ME", "Period_ME"])
     tm.assert_series_equal(res, exp)
 
 

Diff for: pandas/tests/arithmetic/test_datetime64.py

@@ -173,8 +173,8 @@ class TestDatetime64SeriesComparison:
                 [NaT, NaT, Timedelta("3 days")],
             ),
             (
-                [Period("2011-01", freq="M"), NaT, Period("2011-03", freq="M")],
-                [NaT, NaT, Period("2011-03", freq="M")],
+                [Period("2011-01", freq="ME"), NaT, Period("2011-03", freq="ME")],
+                [NaT, NaT, Period("2011-03", freq="ME")],
             ),
         ],
     )
@@ -218,7 +218,7 @@ def test_nat_comparisons(
         [
             [Timestamp("2011-01-01"), NaT, Timestamp("2011-01-03")],
             [Timedelta("1 days"), NaT, Timedelta("3 days")],
-            [Period("2011-01", freq="M"), NaT, Period("2011-03", freq="M")],
+            [Period("2011-01", freq="ME"), NaT, Period("2011-03", freq="ME")],
         ],
     )
     @pytest.mark.parametrize("dtype", [None, object])
@@ -1078,7 +1078,7 @@ def test_dt64arr_add_dtlike_raises(self, tz_naive_fixture, box_with_array):
     # Note: freq here includes both Tick and non-Tick offsets; this is
     #  relevant because historically integer-addition was allowed if we had
     #  a freq.
-    @pytest.mark.parametrize("freq", ["H", "D", "W", "M", "MS", "Q", "B", None])
+    @pytest.mark.parametrize("freq", ["H", "D", "W", "ME", "MS", "Q", "B", None])
     @pytest.mark.parametrize("dtype", [None, "uint8"])
     def test_dt64arr_addsub_intlike(
         self, dtype, box_with_array, freq, tz_naive_fixture