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REGR: Fix conversion of mixed dtype DataFrame to numpy str #35473

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Merged
merged 5 commits into from
Aug 7, 2020
Merged

REGR: Fix conversion of mixed dtype DataFrame to numpy str #35473

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661c308
Handle str better
dsaxton Jul 30, 2020
73db693
Doc and test
dsaxton Jul 30, 2020
6f45bca
Make an elif
dsaxton Aug 7, 2020
726dc83
Merge remote-tracking branch 'upstream/master' into to_numpy-regr
dsaxton Aug 7, 2020
61beac7
Add back import
dsaxton Aug 7, 2020
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2 changes: 1 addition & 1 deletion doc/source/whatsnew/v1.1.1.rst
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Expand Up @@ -15,7 +15,7 @@ including other versions of pandas.
Fixed regressions
~~~~~~~~~~~~~~~~~

-
- Regression where :meth:`DataFrame.to_numpy` would raise a ``RuntimeError`` for mixed dtypes when converting to ``str`` (:issue:`35455`)
-
-

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2 changes: 2 additions & 0 deletions pandas/core/frame.py
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Expand Up @@ -1370,6 +1370,8 @@ def to_numpy(
result = self._mgr.as_array(
transpose=self._AXIS_REVERSED, dtype=dtype, copy=copy, na_value=na_value
)
if result.dtype is not dtype:
result = np.array(result, dtype=dtype, copy=False)

return result

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2 changes: 1 addition & 1 deletion pandas/core/internals/managers.py
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Expand Up @@ -847,7 +847,7 @@ def _interleave(self, dtype=None, na_value=lib.no_default) -> np.ndarray:
# Give EAs some input on what happens here. Sparse needs this.
if isinstance(dtype, SparseDtype):
dtype = dtype.subtype
elif is_extension_array_dtype(dtype):
elif is_extension_array_dtype(dtype) or is_dtype_equal(dtype, str):
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are you sure this is actually hit?

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Yes, this is to avoid initializing result as np.empty(dtype=str) which was creating an array with dtype "<U1" and then breaking things.

Before the change that caused this regression the dtype was always being set to the inferred dtype from _interleaved_dtype (object in this case), so here I'm trying to make sure that this still happens.

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make this a separate elif as it is very confusing here the way it is written

dtype = "object"

result = np.empty(self.shape, dtype=dtype)
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7 changes: 7 additions & 0 deletions pandas/tests/frame/test_api.py
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Expand Up @@ -367,6 +367,13 @@ def test_to_numpy_copy(self):
assert df.to_numpy(copy=False).base is arr
assert df.to_numpy(copy=True).base is not arr

def test_to_numpy_mixed_dtype_to_str(self):
# https://github.com/pandas-dev/pandas/issues/35455
df = pd.DataFrame([[pd.Timestamp("2020-01-01 00:00:00"), 100.0]])
result = df.to_numpy(dtype=str)
expected = np.array([["2020-01-01 00:00:00", "100.0"]], dtype=str)
tm.assert_numpy_array_equal(result, expected)

def test_swapaxes(self):
df = DataFrame(np.random.randn(10, 5))
tm.assert_frame_equal(df.T, df.swapaxes(0, 1))
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