BUG: Join did not work correctly when one MultiIndex had only one level #37208
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This pull request is stale because it has been open for thirty days with no activity. Please update or respond to this comment if you're still interested in working on this. |
jreback
requested changes
Jan 1, 2021
doc/source/whatsnew/v1.2.0.rst
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| @@ -474,6 +474,7 @@ Reshaping | |||
| - Bug in func :meth:`crosstab` when using multiple columns with ``margins=True`` and ``normalize=True`` (:issue:`35144`) | |||
| - Bug in :meth:`DataFrame.agg` with ``func={'name':<FUNC>}`` incorrectly raising ``TypeError`` when ``DataFrame.columns==['Name']`` (:issue:`36212`) | |||
| - Bug in :meth:`Series.transform` would give incorrect results or raise when the argument ``func`` was dictionary (:issue:`35811`) | |||
| - Bug in :func:`join` over :class:`MultiIndex` returned wrong result, when one of both indexes had only one level (:issue:`36909`) | |||
� Conflicts: � doc/source/whatsnew/v1.2.0.rst � pandas/core/indexes/base.py � pandas/tests/indexes/multi/test_drop.py � pandas/tests/reshape/merge/test_join.py
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Done |
jreback
requested changes
Jan 3, 2021
| @@ -815,3 +815,20 @@ def test_join_cross(input_col, output_cols): | |||
| result = left.join(right, how="cross", lsuffix="_x", rsuffix="_y") | |||
| expected = DataFrame({output_cols[0]: [1, 1, 3, 3], output_cols[1]: [3, 4, 3, 4]}) | |||
| tm.assert_frame_equal(result, expected) | |||
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| @pytest.mark.parametrize("how", ["left", "right", "inner", "outer"]) | |||
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don't we have a fixture for this?
pandas/core/indexes/base.py
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| @@ -1672,7 +1672,7 @@ def _drop_level_numbers(self, levnums: List[int]): | |||
| Drop MultiIndex levels by level _number_, not name. | |||
| """ | |||
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| if not levnums: | |||
| if not levnums and (len(self) > 1 or not isinstance(self, ABCMultiIndex)): | |||
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this len(self) > 1 is a very odd check, what is the intent?
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Seems to be no longer necessary. Code changed quite a bit since I implemented this. Removed it.
� Conflicts: � doc/source/whatsnew/v1.3.0.rst
jreback
approved these changes
Jan 3, 2021
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@jreback green |
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thanks |
luckyvs1
pushed a commit
to luckyvs1/pandas
that referenced
this pull request
Jan 20, 2021
…el (pandas-dev#37208) * BUG: join did not work correctly when one MultiIndex had only one level * Change pr number * Move whatsnew * Remove pd * Usef fixture * Remove len self
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black pandasgit diff upstream/master -u -- "*.py" | flake8 --diffdroplevelforMultiIndexreturns anIndexwhen the resultingMultiIndexhad only one level. But if the input had only one level and no level should be dropped, the return was aMultiIndex. This did not seem consistent, so I changed it, that in this case an Index would be returned too. If this is not the desired behavior, we could fix thejoinproblems after calling this functions.If this is not desired, we should add a note to the docstring, that the return for
droplevelis a MultiIndex, if no level is dropped.