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Python · performance

prefer-module-level-constant

python:prefer-module-level-constant

Literal-only collections and compiled regular expressions built inside a function should be module-level constants.

Code
SARJ039
Default
error
Fix
none
Languages
python

Why

Rebuilding immutable data or a constant regex on every call wastes work and obscures its static nature.

Fix

Define the value once at module scope and reference that constant from the function.

Before / after

Executed by this rule’s unit tests.

Before

Static list rebuilt in a function

service.py · focus
def handle(value):
    allowed = ["a", "b", "c"]
    return value in allowed

After

Static list defined once

service.py · focus
ALLOWED = ["a", "b", "c"]

def handle(value):
    return value in ALLOWED

Limits

  • Test and generated files are excluded.
  • Only proven literal-only collections of at least three elements and constant `re.compile` calls are reported.