Comment

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

antlion@lemmy.dbzer0.com ⁨11⁩ ⁨months⁩ ago

Could also compare against:

if not len(mylist)

That way this version isn’t evaluating two functions. The bool evaluation of an integer is false when zero, otherwise true.

Sort:hotnew top

sugar_in_your_tea@sh.itjust.works ⁨11⁩ ⁨months⁩ 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.
source
FooBarrington@lemmy.world ⁨11⁩ ⁨months⁩ ago
This is honestly the worst version regarding readability. Don’t rely on implicit coercion, people.

source
- antlion@lemmy.dbzer0.com ⁨11⁩ ⁨months⁩ 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.
  
  source
  - FooBarrington@lemmy.world ⁨11⁩ ⁨months⁩ 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:.
    
    source