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BUG: fix empty suffix and prefix handling in pyarrow string methods #63395

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Merged
jorisvandenbossche merged 14 commits into from
Dec 18, 2025
+16 −2
Merged

BUG: fix empty suffix and prefix handling in pyarrow string methods #63395

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c64ef05
BUG: fix empty suffix and prefix handling in pyarrow string methods
vkverma9534 Dec 17, 2025
74fb4f9
BUG: add tests for empty prefix and suffix
vkverma9534 Dec 17, 2025
a1da54e
BUG: handle empty prefix in pyarrow-backed removeprefix
vkverma9534 Dec 17, 2025
f71a75c
BUG: fix empty prefix/suffix handling in pyarrow-backed string methods
vkverma9534 Dec 17, 2025
2ec810d
BUG: fix removeprefix/removesuffix for empty strings in pyarrow backend
vkverma9534 Dec 17, 2025
9a526ea
Fix for failing cases
vkverma9534 Dec 17, 2025
e733bfb
fix for failing tests
vkverma9534 Dec 17, 2025
f8d2c6f
style: fix indentation
vkverma9534 Dec 18, 2025
2977a04
Apply suggestion from @jorisvandenbossche
jorisvandenbossche Dec 18, 2025
142a609
Apply suggestion from @jorisvandenbossche
jorisvandenbossche Dec 18, 2025
78af6fa
Apply suggestion from @jorisvandenbossche
jorisvandenbossche Dec 18, 2025
1cdc3df
fixup style
jorisvandenbossche Dec 18, 2025
2f302d4
return shallow copy
jorisvandenbossche Dec 18, 2025
4def7fa
Fix type check error by avoiding copy() in ArrowStringArrayMixin
vkverma9534 Dec 18, 2025
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28 changes: 18 additions & 10 deletions pandas/core/arrays/_arrow_string_mixins.py
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Original file line number Diff line number Diff line change
Expand Up @@ -201,18 +201,26 @@ def _str_title(self) -> Self:

def _str_swapcase(self) -> Self:
return self._from_pyarrow_array(pc.utf8_swapcase(self._pa_array))
def _str_removeprefix(self, prefix: str):
if prefix == "":
return self
starts_with = pc.starts_with(self._pa_array, pattern=prefix)
removed = pc.utf8_slice_codeunits(self._pa_array, len(prefix))
result = pc.if_else(starts_with, removed, self._pa_array)
return self._from_pyarrow_array(result)


def _str_removesuffix(self, suffix: str):
if suffix == "":
return self
ends_with = pc.ends_with(self._pa_array, pattern=suffix)
removed = pc.utf8_slice_codeunits(self._pa_array, 0, stop=-len(suffix))
result = pc.if_else(ends_with, removed, self._pa_array)
return self._from_pyarrow_array(result)



def _str_removeprefix(self, prefix: str):
starts_with = pc.starts_with(self._pa_array, pattern=prefix)
removed = pc.utf8_slice_codeunits(self._pa_array, len(prefix))
result = pc.if_else(starts_with, removed, self._pa_array)
return self._from_pyarrow_array(result)

def _str_removesuffix(self, suffix: str):
ends_with = pc.ends_with(self._pa_array, pattern=suffix)
removed = pc.utf8_slice_codeunits(self._pa_array, 0, stop=-len(suffix))
result = pc.if_else(ends_with, removed, self._pa_array)
return self._from_pyarrow_array(result)
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@jorisvandenbossche jorisvandenbossche Dec 17, 2025 •
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Suggested change
def _str_removeprefix(self, prefix: str):
if prefix == "":
return self
starts_with = pc.starts_with(self._pa_array, pattern=prefix)
removed = pc.utf8_slice_codeunits(self._pa_array, len(prefix))
result = pc.if_else(starts_with, removed, self._pa_array)
return self._from_pyarrow_array(result)
def _str_removesuffix(self, suffix: str):
if suffix == "":
return self
ends_with = pc.ends_with(self._pa_array, pattern=suffix)
removed = pc.utf8_slice_codeunits(self._pa_array, 0, stop=-len(suffix))
result = pc.if_else(ends_with, removed, self._pa_array)
return self._from_pyarrow_array(result)
def _str_removeprefix(self, prefix: str):
starts_with = pc.starts_with(self._pa_array, pattern=prefix)
removed = pc.utf8_slice_codeunits(self._pa_array, len(prefix))
result = pc.if_else(starts_with, removed, self._pa_array)
return self._from_pyarrow_array(result)
def _str_removesuffix(self, suffix: str):
ends_with = pc.ends_with(self._pa_array, pattern=suffix)
removed = pc.utf8_slice_codeunits(self._pa_array, 0, stop=-len(suffix))
result = pc.if_else(ends_with, removed, self._pa_array)
return self._from_pyarrow_array(result)
def _str_removeprefix(self, prefix: str):
if prefix == "":
return self
starts_with = pc.starts_with(self._pa_array, pattern=prefix)
removed = pc.utf8_slice_codeunits(self._pa_array, len(prefix))
result = pc.if_else(starts_with, removed, self._pa_array)
return self._from_pyarrow_array(result)
def _str_removesuffix(self, suffix: str):
if prefix == "":
return self
ends_with = pc.ends_with(self._pa_array, pattern=suffix)
removed = pc.utf8_slice_codeunits(self._pa_array, 0, stop=-len(suffix))
result = pc.if_else(ends_with, removed, self._pa_array)
return self._from_pyarrow_array(result)

I think this should fix it
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@vkverma9534 vkverma9534 Dec 18, 2025

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I made those fixes as you suggested (added suffix=="" condition in _str_removesuffix ) still two checks seem to be failing, is that okay?

def _str_startswith(
self, pat: str | tuple[str, ...], na: Scalar | lib.NoDefault = lib.no_default
Expand Down
16 changes: 14 additions & 2 deletions pandas/tests/strings/test_strings.py
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Original file line number Diff line number Diff line change
Expand Up @@ -544,7 +544,12 @@ def test_strip_lstrip_rstrip_args(any_string_dtype, method, exp):


@pytest.mark.parametrize(
"prefix, expected", [("a", ["b", " b c", "bc"]), ("ab", ["", "a b c", "bc"])]
"prefix, expected",
[
("a", ["b", " b c", "bc"]),
("ab", ["", "a b c", "bc"]),
("", ["ab", "a b c", "bc"]),
],
)
def test_removeprefix(any_string_dtype, prefix, expected):
ser = Series(["ab", "a b c", "bc"], dtype=any_string_dtype)
Expand All @@ -554,7 +559,12 @@ def test_removeprefix(any_string_dtype, prefix, expected):


@pytest.mark.parametrize(
"suffix, expected", [("c", ["ab", "a b ", "b"]), ("bc", ["ab", "a b c", ""])]
"suffix, expected",
[
("c", ["ab", "a b ", "b"]),
("bc", ["ab", "a b c", ""]),
("", ["ab", "a b c", "bc"]),
],
)
def test_removesuffix(any_string_dtype, suffix, expected):
ser = Series(["ab", "a b c", "bc"], dtype=any_string_dtype)
Expand All @@ -563,6 +573,8 @@ def test_removesuffix(any_string_dtype, suffix, expected):
tm.assert_series_equal(result, ser_expected)




def test_string_slice_get_syntax(any_string_dtype):
ser = Series(
["YYY", "B", "C", "YYYYYYbYYY", "BYYYcYYY", np.nan, "CYYYBYYY", "dog", "cYYYt"],
Expand Down
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