Fix incosistent behavior of loc-set with 2 indexes to Series #59333

[anzber]

• closes BUG: locset with Series as column key fails inconsistently #59933
• Tests added and passed
• All code checks passed
• Added an entry in the latest doc/source/whatsnew/vX.X.X.rst file if fixing a bug or adding a new feature.

Comments about pull-request:

1. Fixed case with inconsistent behavior of different indexes

>>> df = pd.DataFrame([[1, 2, 3], [4, 5, 6], [7, 8, 9]], columns=list("ABC"))
>>> df.loc[:, ['A', 'B', 'C']] = pd.Series([10, 20, 30]) 
#before fix
>>> df
    A   B   C
0  10  20  30
1  10  20  30
2  10  20  30
#after fix
>>> df
    A   B   C
0  10  10  10
1  20  20  20
2  30  30  30

Inconsistance with case:

#before and after fix (no changes)
>>> df = pd.DataFrame([[1, 2, 3], [4, 5, 6], [7, 8, 9]], columns=list("ABC"))
>>> df.loc[df['A']>0, ['A', 'B', 'C']] = pd.Series([10, 20, 30]) 
>>> df
    A   B   C
0  10  10  10
1  20  20  20
2  30  30  30

2. Fixed initial issue. And now it works consistently with test_multi_assign_broadcasting_rhs like this

>>> df = pd.DataFrame([[1, 2, 3], [4, 5, 6]], columns=list("ABC"))
>>> df.loc[:, pd.Series(['A', 'B', 'C'])] = pd.Series([10, 20, 30])
#before fix - FAIL
#after fix 
>>> df
    A   B   C
0  10  10  10
1  20  20  20

pandas/pandas/tests/indexing/test_indexing.py

Lines 475 to 492 in 05fa958

	def test_multi_assign_broadcasting_rhs(self):
	# broadcasting on the rhs is required
	df = DataFrame(
	{
	"A": [1, 2, 0, 0, 0],
	"B": [0, 0, 0, 10, 11],
	"C": [0, 0, 0, 10, 11],
	"D": [3, 4, 5, 6, 7],
	}
	)
	expected = df.copy()
	mask = expected["A"] == 0
	for col in ["A", "B"]:
	expected.loc[mask, col] = df["D"]
	df.loc[df["A"] == 0, ["A", "B"]] = df["D"].copy()
	tm.assert_frame_equal(df, expected)

[rhshadrach]

CI is fixed now, can you merge main.

[rhshadrach]

@mroeschke - I'm not too familiar with this code, this looks okay but am not certain. Can you take a look as well?

[rhshadrach]

I think you can use axes[1][indexer[1]] instead of .loc.

[anzber]

I've made changes requested, but failed test appeared

[rhshadrach]

@anzber - test failures look related. Can you also give this PR an informative title? It is helpful to have titles that give devs a sense of what the PR is doing without having to go open the issue.

[anzber]

@anzber - test failures look related. Can you also give this PR an informative title? It is helpful to have titles that give devs a sense of what the PR is doing without having to go open the issue.

@rhshadrach added more information to title. Thank You for reviewing the code.

[rhshadrach]

added more information to title

The title of this PR is still Fix issue #59333.

Will also need a note in the whatsnew for v3.0.0.

[anzber]

@rhshadrach
I've found a new problem related the issue

This code fails, but shouldn't :

df33 = pd.DataFrame([[1, 2, 3], [4, 5, 6], [7, 8, 9]], columns = list("ABC"))
df33.loc[:, pd.Series({"A": True, "B": True, "C": False})] = pd.Series([10, 20, 30])
df33

[github-actions]

This pull request is stale because it has been open for thirty days with no activity. Please update and respond to this comment if you're still interested in working on this.

[mroeschke]

Thanks for the pull request, but it appears to have gone stale. If interested in continuing, please merge in the main branch, address any review comments and/or failing tests, and we can reopen.

[rhshadrach]

Reopening (ref: #60621)