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BUG: Impossible creation of array with dtype=string #61263

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3474043
DOC: Update warning in Index.values docstring to clarify index modifi…
Manju080 Mar 6, 2025
d070b06
DOC: Update warning in Index.values docstring to clarify index modifi…
Manju080 Mar 7, 2025
b00ba12
Update pandas/core/indexes/base.py
Manju080 Mar 8, 2025
390c8be
DOC : Fixing the whitespace which was causing error
Manju080 Mar 10, 2025
e58f383
Fixed docstring validation and formatting issues
Manju080 Mar 11, 2025
a505d35
BUG: Fix array creation for string dtype with inconsistent list lengt…
Manju080 Apr 9, 2025
6f5c4d4
BUG: Fix array creation for string dtype with inconsistent list lengt…
Manju080 Apr 9, 2025
fc4653d
BUG fix GH#61155 v2
Manju080 Apr 15, 2025
ae36cf7
BUG fix GH#61155 with test case for list of lists handling
Manju080 Apr 15, 2025
fb965e7
Fix formatting in test_string_array.py (pre-commit autofix)
Manju080 Apr 16, 2025
d3bbeaf
[pre-commit.ci] auto fixes from pre-commit.com hooks
pre-commit-ci[bot] Apr 16, 2025
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5 changes: 4 additions & 1 deletion pandas/_libs/lib.pyx
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Original file line number Diff line number Diff line change
Expand Up @@ -769,7 +769,10 @@ cpdef ndarray[object] ensure_string_array(
return out
arr = arr.to_numpy(dtype=object)
elif not util.is_array(arr):
arr = np.array(arr, dtype="object")
# GH#61155: Guarantee a 1-d result when array is a list of lists
input_arr = arr
arr = np.empty(len(arr), dtype="object")
arr[:] = input_arr

result = np.asarray(arr, dtype="object")

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2 changes: 2 additions & 0 deletions pandas/core/arrays/string_.py
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Original file line number Diff line number Diff line change
Expand Up @@ -655,6 +655,8 @@ def _from_sequence(
# zero_copy_only to True which caused problems see GH#52076
scalars = np.array(scalars)
# convert non-na-likes to str, and nan-likes to StringDtype().na_value
if isinstance(scalars, list) and all(isinstance(x, list) for x in scalars):
scalars = [str(x) for x in scalars]
Comment on lines +658 to +659
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@rhshadrach rhshadrach Apr 13, 2025 •
edited
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Instead of this, can you modify ensure_string_array in pandas._libs.lib.pyx as follows. Instead of

elif not util.is_array(arr):
    arr = np.array(arr, dtype="object")

do

elif not util.is_array(arr):
    # GH#61155: Guarantee a 1-d result when array is a list of lists
    arr = np.empty(len(array), dtype="object")
    arr[:] = array

Will has almost no performance impact.

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Thank you very much for the suggestions, I have made the necessary changes as per the guidance.

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Thanks for making the update. The changes in this file should now be reverted.

result = lib.ensure_string_array(scalars, na_value=na_value, copy=copy)

# Manually creating new array avoids the validation step in the __init__, so is
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4 changes: 4 additions & 0 deletions pandas/core/indexes/base.py
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Original file line number Diff line number Diff line change
Expand Up @@ -4912,6 +4912,10 @@ def values(self) -> ArrayLike:
:meth:`Index.to_numpy`, depending on whether you need
a reference to the underlying data or a NumPy array.

.. versionchanged:: 3.0.0

The returned array is read-only.

Returns
-------
array: numpy.ndarray or ExtensionArray
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4 changes: 4 additions & 0 deletions pandas/tests/arrays/test_string_array.py
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@@ -0,0 +1,4 @@
import pandas as pd

print(pd.array([list("test"), list("words")], dtype="string"))
print(pd.array([list("test"), list("word")], dtype="string"))
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