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REGR: read_csv and nullable dtypes fails if dtype is specified #49147

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Merged
merged 1 commit into from
Oct 17, 2022
Merged

REGR: read_csv and nullable dtypes fails if dtype is specified #49147

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3 changes: 3 additions & 0 deletions pandas/_libs/parsers.pyx
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Original file line number Diff line number Diff line change
Expand Up @@ -1414,6 +1414,9 @@ def _maybe_upcast(arr, use_nullable_dtypes: bool = False):
-------
The casted array.
"""
if is_extension_array_dtype(arr.dtype):
return arr

na_value = na_values[arr.dtype]

if issubclass(arr.dtype.type, np.integer):
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11 changes: 11 additions & 0 deletions pandas/tests/io/parser/dtypes/test_dtypes_basic.py
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Expand Up @@ -466,3 +466,14 @@ def test_use_nullabla_dtypes_string(all_parsers, storage):
}
)
tm.assert_frame_equal(result, expected)


def test_use_nullable_dtypes_ea_dtype_specified(all_parsers):
# GH#491496
data = """a,b
1,2
"""
parser = all_parsers
result = parser.read_csv(StringIO(data), dtype="Int64", use_nullable_dtypes=True)
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Do we have tests for dtype="int64", use_nullable_dtypes=True?

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test_use_nullabla_dtypes_and_dtype Same file

expected = DataFrame({"a": [1], "b": 2}, dtype="Int64")
tm.assert_frame_equal(result, expected)