From df913e79470e22ede1fec185a4ff224631c38f42 Mon Sep 17 00:00:00 2001 From: Natalia Mokeeva <91160475+natmokval@users.noreply.github.com> Date: Mon, 4 Dec 2023 12:14:57 +0100 Subject: [PATCH] ENH: Raise TypeError when converting DatetimeIndex to PeriodIndex with invalid period frequency (#56243) --- doc/source/whatsnew/v2.2.0.rst | 1 + pandas/core/arrays/period.py | 7 ++++++- pandas/tests/indexes/datetimes/methods/test_to_period.py | 8 ++++++++ 3 files changed, 15 insertions(+), 1 deletion(-) diff --git a/doc/source/whatsnew/v2.2.0.rst b/doc/source/whatsnew/v2.2.0.rst index ade87c4215a38..8bd9ac1aa366c 100644 --- a/doc/source/whatsnew/v2.2.0.rst +++ b/doc/source/whatsnew/v2.2.0.rst @@ -226,6 +226,7 @@ Other enhancements - Allow passing ``read_only``, ``data_only`` and ``keep_links`` arguments to openpyxl using ``engine_kwargs`` of :func:`read_excel` (:issue:`55027`) - DataFrame.apply now allows the usage of numba (via ``engine="numba"``) to JIT compile the passed function, allowing for potential speedups (:issue:`54666`) - Implement masked algorithms for :meth:`Series.value_counts` (:issue:`54984`) +- Improved error message that appears in :meth:`DatetimeIndex.to_period` with frequencies which are not supported as period frequencies, such as "BMS" (:issue:`56243`) - Improved error message when constructing :class:`Period` with invalid offsets such as "QS" (:issue:`55785`) .. --------------------------------------------------------------------------- diff --git a/pandas/core/arrays/period.py b/pandas/core/arrays/period.py index 57b244e8d02e9..a8c21cfbb6e2f 100644 --- a/pandas/core/arrays/period.py +++ b/pandas/core/arrays/period.py @@ -1174,7 +1174,12 @@ def dt64arr_to_periodarr( reso = get_unit_from_dtype(data.dtype) freq = Period._maybe_convert_freq(freq) - base = freq._period_dtype_code + try: + base = freq._period_dtype_code + except (AttributeError, TypeError): + # AttributeError: _period_dtype_code might not exist + # TypeError: _period_dtype_code might intentionally raise + raise TypeError(f"{freq.name} is not supported as period frequency") return c_dt64arr_to_periodarr(data.view("i8"), base, tz, reso=reso), freq diff --git a/pandas/tests/indexes/datetimes/methods/test_to_period.py b/pandas/tests/indexes/datetimes/methods/test_to_period.py index aa217e895c30a..2c68ddd3d3d15 100644 --- a/pandas/tests/indexes/datetimes/methods/test_to_period.py +++ b/pandas/tests/indexes/datetimes/methods/test_to_period.py @@ -230,3 +230,11 @@ def test_to_period_nofreq(self): idx = DatetimeIndex(["2000-01-01", "2000-01-02", "2000-01-03"]) assert idx.freqstr is None tm.assert_index_equal(idx.to_period(), expected) + + @pytest.mark.parametrize("freq", ["2BMS", "1SME-15"]) + def test_to_period_offsets_not_supported(self, freq): + # GH#56243 + msg = f"{freq[1:]} is not supported as period frequency" + ts = date_range("1/1/2012", periods=4, freq=freq) + with pytest.raises(TypeError, match=msg): + ts.to_period()