`cupyx.scipy.fft` is not compatible with `scipy.fft`

In SciPy, scipy.fft is accessible after importing scipy.

$ python -c 'import scipy; print(scipy.fft)'
<module 'scipy.fft' from '/home/niboshi/.pyenv/versions/3.8.0/lib/python3.8/site-packages/scipy/fft/__init__.py'>

cupyx.scipy.fft is not accessible after importing cupyx.scipy.

$ python -c 'import cupyx.scipy; print(cupyx.scipy.fft)'
Traceback (most recent call last):
  File "<string>", line 1, in <module>
AttributeError: module 'cupyx.scipy' has no attribute 'fft'

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(What follows is the initial version of this post, where I used an old version of SciPy (1.3.3) and it doesn’t apply to the newest one).

In SciPy, scipy.fft is accessible after importing scipy and is a function.

$ python -c 'import scipy; print(scipy.fft)'
<function fft at 0x7fab290c95e0>

cupyx.scipy.fft is not accessible after importing cupyx.scipy.

$ python -c 'import cupyx.scipy; print(cupyx.scipy.fft)'
Traceback (most recent call last):
 File "<string>", line 1, in <module>
AttributeError: module 'cupyx.scipy' has no attribute 'fft'

Further, it’s not a function. You have to spell out as cupyx.scipy.fft.fft.

$ python -c 'import cupyx.scipy.fft; print(cupyx.scipy.fft)'
<module 'cupyx.scipy.fft' from '/data2/work/w/repos/cupy/cupyx/scipy/fft/__init__.py'>

$ python -c 'import cupyx.scipy.fft; print(cupyx.scipy.fft.fft)'
<function fft at 0x7f4787ea91f0>

[grlee77]

This function scipy.fft is just numpy.fft.fft. There are a number of other NumPy functions that get imported into the root SciPy namespace as well, but all of them have recently been deprecated: https://github.com/scipy/scipy/pull/10290.

We would like to remove all of them as it is odd to provide functions from a separate library in the public API. Most of them may not be removed for some time, but the current plan is to remove scipy.fft from 1.5 so we don’t have this weird hack where there is both a function and module with the same name!

[niboshi]

https://github.com/scipy/scipy/issues/11264#issuecomment-568426924

Closing as it’s confirmed we don’t have to follow SciPy’s behavior.