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BUG: iterating on a subset of columns in a GroupBy object (#44821) #44947

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Dec 23, 2021
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2 changes: 1 addition & 1 deletion pandas/core/groupby/groupby.py
Original file line number Diff line number Diff line change
Expand Up @@ -758,7 +758,7 @@ def __iter__(self) -> Iterator[tuple[Hashable, NDFrameT]]:
Generator yielding sequence of (name, subsetted object)
for each group
"""
return self.grouper.get_iterator(self.obj, axis=self.axis)
return self.grouper.get_iterator(self._selected_obj, axis=self.axis)


# To track operations that expand dimensions, like ohlc
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11 changes: 11 additions & 0 deletions pandas/tests/groupby/test_indexing.py
Original file line number Diff line number Diff line change
Expand Up @@ -285,3 +285,14 @@ def test_column_axis(column_group_df):
expected = column_group_df.iloc[:, [1, 3]]

tm.assert_frame_equal(result, expected)


def test_columns_on_iter():
# GitHub issue #44821
df = pd.DataFrame({k: range(10) for k in "ABC"})

# Group-by and select columns
cols = ["A", "B"]
for _, dg in df.groupby(df.A < 4)[cols]:
tm.assert_index_equal(dg.columns, pd.Index(cols))
assert "C" not in dg.columns
2 changes: 1 addition & 1 deletion pandas/tests/window/test_base_indexer.py
Original file line number Diff line number Diff line change
Expand Up @@ -437,7 +437,7 @@ def test_rolling_groupby_with_fixed_forward_many(group_keys, window_size):
result = df.groupby("a")["b"].rolling(window=indexer, min_periods=1).sum()
result.index.names = ["a", "c"]

groups = df.groupby("a")[["a", "b"]]
groups = df.groupby("a")[["a", "b", "c"]]
manual = concat(
[
g.assign(
Expand Down