Stream not closed (ARCH2081)

Key python.performance.stream-not-closed · Severity error · Category performance

A stream opened with open but used without with is not closed on error or early return, leaking the file descriptor. Use a context manager.

Incorrect

def read_config(path):
    f = open(path)
    data = f.read()
    return parse(data)

Correct

def read_config(path):
    with open(path) as f:
        data = f.read()
    return parse(data)

Fix

Open streams with with open(...) as f: so they close automatically on block exit.