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Python Performance: Why 'if not list' is 2x Faster Than Using len()
(blog.codingconfessions.com)
this post was submitted on 12 Apr 2025
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Yea and then you use "not" with a variable name that does not make it obvious that it is a list and another person who reads the code thinks it is a bool. Hell a couple of months later you yourself wont even understand that it is a list. Moreover "not" will not throw an error if you don't use an sequence/collection there as you should but len will.
You should not sacrifice code readability and safety for over optimization, this is phyton after all I don't think list lengths will be your bottle neck.
In my experience, if you didn't write the function that creates the list, there's a solid chance it could be
Nonetoo, and if you try to check the length ofNone, you get an error. This is also why returningNonewhen a function fails is bad practice IMO, but that doesn't seem to stop my coworkers.Passing None to a function expecting a list is the error...