Large collection copy (ARCH2086)

Key python.performance.large-collection-copy · Severity info · Category performance

Fully materializing a generator with list() just to iterate it pulls every element into memory. Stream over the generator directly instead.

Incorrect

def total_amount(rows):
    items = list(r.amount for r in rows)
    return sum(items)

Correct

def total_amount(rows):
    return sum(r.amount for r in rows)

Fix

Do not list() generators you only iterate; stream over them directly.