Python Performance: Why 'if not list' is 2x Faster Than Using len()
Python Performance: Why 'if not list' is 2x Faster Than Using len()
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Python Performance: Why 'if not list' is 2x Faster Than Using len()
150 comments
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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.
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That's worse. IMO, solve this problem with two things:
- type hint
mylistaslist | Noneor justlist - 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
Nonevs empty isn't an important distinction here. - type hint
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This is honestly the worst version regarding readability. Don't rely on implicit coercion, people.
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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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Yes, the first example does the same thing, but there's still less to mentally parse. Ideally you should just use
if len(mylist) == 0:.
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150 comments