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BUG/TST Added support for empty dictionary when passed to agg for gro… #50192

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BUG/TST Added support for empty dictionary when passed to agg for gro… #50192

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BUG/TST Added support for empty dictionary when passed to agg for gro…
eshanjain1 Dec 11, 2022
2c22e12
Fixed pre-commit error.
eshanjain1 Dec 11, 2022
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18 changes: 13 additions & 5 deletions pandas/core/apply.py
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Original file line number Diff line number Diff line change
Expand Up @@ -413,11 +413,19 @@ def agg_dict_like(self) -> DataFrame | Series:
keys_to_use = ktu

axis: AxisInt = 0 if isinstance(obj, ABCSeries) else 1
result = concat(
{k: results[k] for k in keys_to_use},
axis=axis,
keys=keys_to_use,
)

# GH 48581 - Adding consistency to empty agg types
if not results:
# return empty DataFrame if results is empty, following pattern
# empty list and tuple
Comment on lines +417 to +420
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I think the comments here can be removed; I think it's clear that the else code path will fail in this case and why we're returning an empty frame.

from pandas import DataFrame

result = DataFrame()
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Does type(selected_object)() work here?

else:
result = concat(
{k: results[k] for k in keys_to_use}, axis=axis, keys=keys_to_use
)

elif any(is_ndframe):
# There is a mix of NDFrames and scalars
raise ValueError(
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9 changes: 9 additions & 0 deletions pandas/tests/groupby/aggregate/test_aggregate.py
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Expand Up @@ -1443,3 +1443,12 @@ def test_agg_of_mode_list(test, constant):
expected = expected.set_index(0)

tm.assert_frame_equal(result, expected)


def test_empty_container_consistency():
df = DataFrame(data={"a": [1, 2], "b": [3, 4], "c": [5, 6]})
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Can you add the GitHub Issue number as a comment in the first line

dict_result = df.groupby("a").agg({})

expected = DataFrame()

tm.assert_frame_equal(dict_result, expected)