On: Python idiom for taking the single item from a list

[statictype]

if L is None then asserting `len(L)==1` throws an exception.

The `if L and` part safeguards against that.

[jemfinch → statictype]

And the point that was made in the other branch of this thread is that if the author intends to guard against None (who knows why?) then he should say, explicitly, "if L is not None". That's what PEP8 recommends precisely to avoid ambiguities such as these.