Redundant list comprehension can be replaced using generator

[DimitriPapadopoulos]

• Closes #xxxx
• Tests added
• User visible changes (including notable bug fixes) are documented in whats-new.rst
• New functions/methods are listed in api.rst

[max-sixty]

thanks for these!

btw @DimitriPapadopoulos if you might be up for doing some more code refinements: the warnings that spew into the Files changed would be great to fix:

NumPy will stop allowing conversion of out-of-bound Python integers to integer arrays.  The conversion of 255 to int8 will fail in the future.
For the old behavior, usually:
    np.array(value).astype(dtype)`
will give the desired result (the cast overflows).

and

invalid value encountered in cast

they're a bit more involved that your previous changes, but I think at least one of them would be tractable — find a test that generates them, try and reproduce the warning, and understand what causes it. for example, I'm guessing somewhere for the first one, our tests are passing in numbers that are too high when we're testing an int8 array...

an alternative would just be limiting the test runs that print warnings to GH to only the core ones, so at least we don't get 10x the messages...

(no obligation ofc, only if you feel interested + want to help out; thank you either way!)