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Improve error message about duplicate columns in df.explode #49264

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Merged
merged 3 commits into from
Oct 26, 2022
Merged

Improve error message about duplicate columns in df.explode #49264

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3c5601a
Improve error message about duplicate columns in df.explode
a-mroz Oct 22, 2022
a7af873
Improve error message for non-unique columns
a-mroz Oct 25, 2022
45e6e64
Improve error message for non-unique columns
a-mroz Oct 25, 2022
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6 changes: 5 additions & 1 deletion pandas/core/frame.py
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Original file line number Diff line number Diff line change
Expand Up @@ -8939,7 +8939,11 @@ def explode(
3 4 1 e
"""
if not self.columns.is_unique:
raise ValueError("columns must be unique")
duplicate_cols = self.columns[self.columns.duplicated()].tolist()
raise ValueError(
"DataFrame columns must be unique. "
+ f"Duplicate columns: {duplicate_cols}"
)

columns: list[Hashable]
if is_scalar(column) or isinstance(column, tuple):
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7 changes: 6 additions & 1 deletion pandas/tests/frame/methods/test_explode.py
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Original file line number Diff line number Diff line change
@@ -1,3 +1,5 @@
import re

import numpy as np
import pytest

Expand All @@ -18,7 +20,10 @@ def test_error():
df.explode(list("AA"))

df.columns = list("AA")
with pytest.raises(ValueError, match="columns must be unique"):
with pytest.raises(
ValueError,
match=re.escape("DataFrame columns must be unique. Duplicate columns: ['A']"),
):
df.explode("A")


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