python 3 password generator

passgen.py

#!/usr/bin/env python3
import string
import random
import sys

if len(sys.argv) != 2:
    print("\033[91mUsage:\033[0m", sys.argv[0], "pass_length")
    sys.exit(1)

pass_len=int(sys.argv[1])

def rand_pass(size=pass_len, chars=string.ascii_uppercase + string.ascii_lowercase + string.digits + string.punctuation):
    return ''.join(random.choice(chars) for _ in range(size))

print(rand_pass())