Unguarded first element (ARCH2078)

Key python.performance.first-or-default-null · Severity warning · Category performance

Accessing [0] of a filtered collection without an emptiness check raises IndexError when the result is empty. Supply a default with next.

Incorrect

def first_admin(users):
    admins = [u for u in users if u.role == "admin"]
    return admins[0]

Correct

def first_admin(users):
    return next((u for u in users if u.role == "admin"), None)

Fix

Take the first match with next(generator, None) so an empty result yields a default.