TYP: tighten Axis

[twoertwein]

axis can only be Literal[0, 1, "index", "columns"]. This PR tightens Axis = Union[int, str] to Axis = Union[int, Literal["index", "columns"]]. A future PR will take care of ints (currently 81 mypy errors).

xref pandas-dev/pandas-stubs#284

[mroeschke]

Note: I think "rows" is accepted too:

pandas/pandas/core/generic.py

Line 489 in bf856a8

_AXIS_TO_AXIS_NUMBER: dict[Axis, int] = {0: 0, "index": 0, "rows": 0}

But I think it's not publicized well and maybe should be deprecated

[twoertwein]

Note: I think "rows" is accepted too:

Yes, the following works:

>>> pd.DataFrame({"A": [1, 2, 3]}, index=["A", "B", "C"]).rename({"A": "0"}, axis="rows")
   A
0  1
B  2
C  3

But I think it's not publicized well and maybe should be deprecated

It is definitely not well publicized - but it feels like an intuitive counterpart to columns. I will look into adding "rows" to Axis (from a typing perspective, not documentation) - can easily be removed if we try to deprecate it later.

[mroeschke]

Thanks @twoertwein