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BUG: Duplicated returns boolean dataframe #25234

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Feb 11, 2019
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BUG: Duplicated returns boolean dataframe #25234

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BUG: Duplicated returns boolean dataframe
Feb 9, 2019
97307dd
Resolved issues brought up in code review
Feb 9, 2019
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2 changes: 2 additions & 0 deletions doc/source/whatsnew/v0.25.0.rst
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Expand Up @@ -68,6 +68,8 @@ Performance Improvements
Bug Fixes
~~~~~~~~~

- Bug in using duplicated with empty dataframes (:issue:`25184`)
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say more like

:meth:DataFrame.duplicate() on empty dataframe was not return a boolean dtyped Series

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this can go in 0.24.2


Categorical
^^^^^^^^^^^

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2 changes: 1 addition & 1 deletion pandas/core/frame.py
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Expand Up @@ -4636,7 +4636,7 @@ def duplicated(self, subset=None, keep='first'):
from pandas._libs.hashtable import duplicated_int64, _SIZE_HINT_LIMIT

if self.empty:
return Series()
return Series(dtype=bool)

def f(vals):
labels, shape = algorithms.factorize(
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6 changes: 6 additions & 0 deletions pandas/tests/frame/test_duplicates.py
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Expand Up @@ -182,6 +182,12 @@ def test_drop_duplicates():
assert df.duplicated(keep=keep).sum() == 0


def test_duplicated_on_empty_frame_gives_back_frame():
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can you add the issue number as a comment here, rename the test to

test_duplicated_on_empty_frame

df = DataFrame(columns=['a', 'b'])
dupes = df.duplicated('a')
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result =
expected =
tm.assert_frame_equal(result, expected)

tm.assert_frame_equal(df[dupes], df)


def test_drop_duplicates_with_duplicate_column_names():
# GH17836
df = DataFrame([
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