diff --git a/doc/source/whatsnew/v3.0.0.rst b/doc/source/whatsnew/v3.0.0.rst index d9d2330f8f11b..afb2f91f65ccd 100644 --- a/doc/source/whatsnew/v3.0.0.rst +++ b/doc/source/whatsnew/v3.0.0.rst @@ -596,6 +596,7 @@ Reshaping ^^^^^^^^^ - Bug in :meth:`DataFrame.join` inconsistently setting result index name (:issue:`55815`) - Bug in :meth:`DataFrame.unstack` producing incorrect results when ``sort=False`` (:issue:`54987`, :issue:`55516`) +- Bug in :meth:`DataFrame.unstack` producing incorrect results when manipulating empty :class:`DataFrame` with an :class:`ExtentionDtype` (:issue:`59123`) Sparse ^^^^^^ diff --git a/pandas/core/reshape/reshape.py b/pandas/core/reshape/reshape.py index 3df55256ec43b..9b7b768fe7adb 100644 --- a/pandas/core/reshape/reshape.py +++ b/pandas/core/reshape/reshape.py @@ -288,21 +288,19 @@ def get_new_values(self, values, fill_value=None): dtype = values.dtype - # if our mask is all True, then we can use our existing dtype - if mask_all: - dtype = values.dtype - new_values = np.empty(result_shape, dtype=dtype) - else: - if isinstance(dtype, ExtensionDtype): - # GH#41875 - # We are assuming that fill_value can be held by this dtype, - # unlike the non-EA case that promotes. - cls = dtype.construct_array_type() - new_values = cls._empty(result_shape, dtype=dtype) + if isinstance(dtype, ExtensionDtype): + # GH#41875 + # We are assuming that fill_value can be held by this dtype, + # unlike the non-EA case that promotes. + cls = dtype.construct_array_type() + new_values = cls._empty(result_shape, dtype=dtype) + if not mask_all: new_values[:] = fill_value - else: + else: + if not mask_all: dtype, fill_value = maybe_promote(dtype, fill_value) - new_values = np.empty(result_shape, dtype=dtype) + new_values = np.empty(result_shape, dtype=dtype) + if not mask_all: new_values.fill(fill_value) name = dtype.name diff --git a/pandas/tests/reshape/test_pivot.py b/pandas/tests/reshape/test_pivot.py index 728becc76b71f..2872b1e29d629 100644 --- a/pandas/tests/reshape/test_pivot.py +++ b/pandas/tests/reshape/test_pivot.py @@ -2769,3 +2769,17 @@ def test_unstack_copy(self, m): result = df.unstack(sort=False) result.iloc[0, 0] = -1 tm.assert_frame_equal(df, df_orig) + + def test_pivot_empty_with_datetime(self): + # GH#59126 + df = DataFrame( + { + "timestamp": Series([], dtype=pd.DatetimeTZDtype(tz="UTC")), + "category": Series([], dtype=str), + "value": Series([], dtype=str), + } + ) + df_pivoted = df.pivot_table( + index="category", columns="value", values="timestamp" + ) + assert df_pivoted.empty