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BUG: clear cache on DataFrame._is_homogeneous_dtype #34937

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Merged
merged 1 commit into from
Jun 24, 2020
Merged

BUG: clear cache on DataFrame._is_homogeneous_dtype #34937

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3 changes: 2 additions & 1 deletion pandas/core/frame.py
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Original file line number Diff line number Diff line change
Expand Up @@ -611,7 +611,8 @@ def _is_homogeneous_type(self) -> bool:
if self._mgr.any_extension_types:
return len({block.dtype for block in self._mgr.blocks}) == 1
else:
return not self._mgr.is_mixed_type
# Note: consolidates inplace
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@jreback jreback Jun 23, 2020 •
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i would rather just push this entire thing to the manager, the frame/series shouldn't really be in charge of this as its accessing internal apis (or at least eventually they will be)

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semi-agree: we shouldnt mix-and-match. But _item_cache pretty much has to be on DataFrame, since that is where the Series objects are created.

return not self._is_mixed_type

@property
def _can_fast_transpose(self) -> bool:
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12 changes: 12 additions & 0 deletions pandas/tests/frame/test_dtypes.py
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Expand Up @@ -233,6 +233,18 @@ def test_constructor_list_str_na(self, string_dtype):
def test_is_homogeneous_type(self, data, expected):
assert data._is_homogeneous_type is expected

def test_is_homogeneous_type_clears_cache(self):
ser = pd.Series([1, 2, 3])
df = ser.to_frame("A")
df["B"] = ser

assert len(df._mgr.blocks) == 2

a = df["B"] # caches lookup
df._is_homogeneous_type # _should_ clear cache
assert len(df._mgr.blocks) == 1
assert df["B"] is not a

def test_asarray_homogenous(self):
df = pd.DataFrame({"A": pd.Categorical([1, 2]), "B": pd.Categorical([1, 2])})
result = np.asarray(df)
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