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

@abhi9u@lemmy.world · 4 days ago

@JustAnotherKay@lemmy.world · 3 days ago

Doesn’t matter what it implies. The entire purpose of programming is to make it so a human doesn’t have to go do something manually.

not x tells me I need to go manually check what type x is in Python.

len(x) == 0 tells me that it’s being type-checked automatically

@sugar_in_your_tea@sh.itjust.works · 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
    ...