DEPR: deprecate Index.__getitem__ with float key #34191
Description
I would propose to deprecate interpreting float numbers as integers in Index __getitem__.
Numpy does (no longer) allow this:
In [1]: a = np.array([1, 2, 3]) In [3]: a[0.0] --------------------------------------------------------------------------- IndexError Traceback (most recent call last) <ipython-input-3-2ec1d2c6d8d4> in <module> ----> 1 a[0.0] IndexError: only integers, slices (`:`), ellipsis (`...`), numpy.newaxis (`None`) and integer or boolean arrays are valid indices With a Series with iloc, we also don't allow this:
In [7]: pd.Series(a).iloc[0.0] ... TypeError: Cannot index by location index with a non-integer key But for Index we do check if the float is integer-like and in that case convert to integer:
In [5]: pd.Index(a)[0.0] Out[5]: 1 However, this is not for all Index subclasses the case, eg:
In [9]: pd.DatetimeIndex(a)[0.0] ... IndexError: only integers, slices (`:`), ellipsis (`...`), numpy.newaxis (`None`) and integer or boolean arrays are valid indices So I think we can simply deprecate this to align Index with numpy/Series/some Index subclasses.