bool([[None, None], [None, None]]) is True? Why?

[steven.daprano]

As far as your second question about flattening the list, the answer remains the same as the answer I gave yesterday about flattening lists:

Any quicker way to flatten a list of pairs?

Your two-line code is beautifully readable, but if you are playing code golf and need to cram everything into one line to save a few characters, you can write the ugly code: [x for y in [[w**2, w**3] for w in lt] for x in y] See also this proposal here: https://mail.python.org/archives/list/python-ideas@python.org/message/7G732VMDWCRMWM4PKRG6ZMUKH7SUC7SH/ although unfortunately it doesn’t exist yet.