Chris Angelico wrote: > On Mon, Sep 12, 2016 at 9:14 PM, Daiyue Weng <daiyuew...@gmail.com> wrote: >> Hi, I found that when I tried to make an equality test on empty like, >> >> if errors == []: >> >> PyCharm always warns me, >> >> Expression can be simplified. >> >> I am wondering what's wrong and how to fix this? >> > > If you know that 'errors' is always going to be a list, you can check > for emptiness thus: > > if not errors:
If I knew that it is always going to be a list or a tuple, I would check its length instead: if len(errors) == 0: Only if I did not know that I would use the “not” keyword, because the latter a) forces a type conversion to “bool”; b) also works with values of other types. > PyCharm recommends this syntax rather than the comparison with a ^^^^^^^^^^^ > newly-created empty list. Are you sure? > Your code has to actually construct and dispose of a list, just for the > comparison. ACK -- PointedEars Twitter: @PointedEars2 Please do not cc me. / Bitte keine Kopien per E-Mail. -- https://mail.python.org/mailman/listinfo/python-list