Discover why 'if not mylist' is twice as fast as 'len(mylist) == 0' by examining CPython's VM instructions and object memory access patterns.
  • sugar_in_your_tea@sh.itjust.worksEnglish
    1·
    3 days ago

    That’s just not true:

    • not x - has an empty value (None, False, [], {}, etc)
    • len(x) == 0 - has a length (list, dict, tuple, etc, or even a custom type implementing __len__)

    You can probably assume it’s iterable, but that’s about it.

    But why assume? You can easily just document the type with a type-hint:

    def do_work(foo: list | None):
    if not foo:
        return
    ...