Extract a single value from a YAML file

yaml_extract.py

#!/usr/bin/env python

from __future__ import print_function

import sys, yaml

if len(sys.argv) < 3:
    print("usage: %s file key ... " % (sys.argv[0]), file=sys.stderr)
    exit(1)

def retrieve_key(f, keys):
    config = yaml.load(f)
    while keys and config:
        key = keys.pop(0)
        try:
            config = config[key]
        except TypeError:
            config = config[int(key)]
    return config

def output_key(f, keys):
    print(retrieve_key(f, keys))

input_file = sys.argv[1]
keys = sys.argv[2:]

if input_file == '-':
    output_key(sys.stdin, keys)
else:
    with open(input_file) as f:
        output_key(f, keys)

Does exit(1) need to be sys.exit(1)?