Comment on Python Performance: Why 'if not list' is 2x Faster Than Using len()

antlion@lemmy.dbzer0.com ⁨6⁩ ⁨days⁩ ago

if not len(mylist)

• FooBarrington@lemmy.world ⁨6⁩ ⁨days⁩ ago

  This is honestly the worst version regarding readability. Don’t rely on implicit coercion, people.

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  • antlion@lemmy.dbzer0.com ⁨6⁩ ⁨days⁩ ago

    But the first example does the same thing for an empty list. I guess the lesson is that if you’re measuring the speed of arbitrary stylistic syntax choices, maybe Python isn’t the best language for you.

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    • FooBarrington@lemmy.world ⁨5⁩ ⁨days⁩ ago

      Yes, the first example does the same thing, but there’s still less to mentally parse. Ideally you should just use if len(my list) == 0:.

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• sugar_in_your_tea@sh.itjust.works ⁨5⁩ ⁨days⁩ ago

  That’s worse. IMO, solve this problem with two things:

  • type hint mylist as list | None or just list
  • use if not mylist:

  The first documents intent and gives you static analysis tools some context to check for type consistency/compatibility, and the second shows that None vs empty isn’t an important distinction here.

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