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FIX-#7569: Fix handling of pyarrow dtype and empty dataframes #7570

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Merged
merged 1 commit into from
May 16, 2025
Merged

FIX-#7569: Fix handling of pyarrow dtype and empty dataframes #7570

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4 changes: 3 additions & 1 deletion modin/core/dataframe/pandas/dataframe/dataframe.py
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Original file line number Diff line number Diff line change
Expand Up @@ -174,7 +174,9 @@ def __init__(
self._row_lengths_cache = row_lengths
self._column_widths_cache = column_widths
self._pandas_backend = pandas_backend
if pandas_backend != "pyarrow":
if pandas_backend != "pyarrow" or len(partitions) == 0:
# If the backend is pyarrow and there are no partitions, the computed dtype otherwise becomes NaN,
# which means we lost the dtype, so actually set it in that case
self.set_dtypes_cache(dtypes)
else:
# In this case, the type precomputation may be incorrect; we need
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7 changes: 7 additions & 0 deletions modin/tests/pandas/dataframe/test_default.py
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Expand Up @@ -18,6 +18,7 @@
import numpy as np
import pandas
import pandas._libs.lib as lib
import pyarrow as pa
import pytest
from numpy.testing import assert_array_equal

Expand Down Expand Up @@ -1533,3 +1534,9 @@ def test_series_does_not_warn_distributing_takes_time():
with warnings.catch_warnings():
warnings.filterwarnings("error", regex, UserWarning)
pd.Series(np.random.randint(1_000_000, size=(2_400_000)))


@pytest.mark.parametrize("dtype", [np.int64, pd.ArrowDtype(pa.int64())])
def test_empty_df_dtypes(dtype):
df = pd.DataFrame({"A": []}, dtype=dtype)
assert df.dtypes["A"] == dtype
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