refactor: ruff rules for comprehensions and performance #34560
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Description
Implement more Python lint rules especially those focused on comprehensions and performance.
%
ruff rule PERF401
manual-list-comprehension (PERF401)
Derived from the Perflint linter.
Fix is sometimes available.
What it does
Checks for
for
loops that can be replaced by a list comprehension.Why is this bad?
When creating a transformed list from an existing list using a for-loop,
prefer a list comprehension. List comprehensions are more readable and
more performant.
Using the below as an example, the list comprehension is ~10% faster on
Python 3.11, and ~25% faster on Python 3.10.
Note that, as with all
perflint
rules, this is only intended as amicro-optimization, and will have a negligible impact on performance in
most cases.
Example
Use instead:
If you're appending to an existing list, use the
extend
method instead:Take care that if the original for-loop uses an assignment expression
as a conditional, such as
if match:=re.match("\d+","123")
, thenthe corresponding comprehension must wrap the assignment
expression in parentheses to avoid a syntax error.
Verification
%
ruff check