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GH-51229: [Python] Raise instead of crashing on unopened resize #51246

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GH-51229: [Python] Raise instead of crashing on unopened resize #51246

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89d4bca
GH-51229: [Python] Check MemoryMappedFile before resize
1fanwang Sep 8, 2026
1a2052d
GH-51229: Assert the value error with pytest.raises
1fanwang Sep 10, 2026
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1 change: 1 addition & 0 deletions python/pyarrow/io.pxi
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Original file line number Diff line number Diff line change
Expand Up @@ -1101,6 +1101,7 @@ cdef class MemoryMappedFile(NativeFile):
----------
new_size : new size in bytes
"""
self._assert_open()
check_status(self.handle.get().Resize(new_size))

def fileno(self):
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5 changes: 5 additions & 0 deletions python/pyarrow/tests/test_io.py
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Expand Up @@ -1216,6 +1216,11 @@ def test_memory_map_resize(tmpdir):
assert f.read() == bytes(arr[:SIZE])


def test_memory_map_resize_uninitialized():
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with pytest.raises(ValueError, match="I/O operation on closed file"):
pa.MemoryMappedFile().resize(0)


Comment on lines +1219 to +1223

@1fanwang 1fanwang Sep 10, 2026

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Keeping it in-process per #51246 (comment); with the fix it raises rather than crashing.

@AlenkaF AlenkaF Sep 11, 2026

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Only the PR description needs an update.

@1fanwang 1fanwang Sep 12, 2026

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The testing description now matches the in-process regression.

def test_memory_zero_length(tmpdir):
path = os.path.join(str(tmpdir), guid())
f = open(path, 'wb')
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