Repeated work in loop (ARCH2072)

Key python.performance.repeated-work-in-loop · Severity info · Category performance

A call or computation that does not depend on the loop variable wastes work when re-evaluated every iteration. Hoist the invariant expression out of the loop.

Incorrect

def filter_active(rows, config):
    result = []
    for row in rows:
        if row.status == config.get_active_status().upper():
            result.append(row)
    return result

Correct

def filter_active(rows, config):
    active = config.get_active_status().upper()
    return [row for row in rows if row.status == active]

Fix

Hoist the loop-invariant computation into a variable before the loop.