Randomly capitalize some text so you can be l33t on social media

randcaps.py

#!/usr/bin/env python3

import argparse
import random
import sys

DEFAULT_PERCENTAGE = 40


def randcaps(text: str, percentage: float = DEFAULT_PERCENTAGE) -> str:
    return ''.join([x.swapcase() if random.uniform(0, 100) < percentage
                    else x for x in text])


if __name__ == '__main__':
    parser = argparse.ArgumentParser(
        description='Randomly capitalize standard input.')
    parser.add_argument('-p', '--percentage', type=float,
                        default=DEFAULT_PERCENTAGE,
                        help='Percentage of letters to capitalize '
                        f'(default: {DEFAULT_PERCENTAGE})')
    parser.add_argument('text', type=str, default=None, nargs="*",
                        help="Text to capitalize instead of standard input.")
    args = parser.parse_args()

    if args.text:
        print(randcaps(' '.join(args.text), percentage=args.percentage))
    else:
        for line in sys.stdin:
            print(randcaps(line.rstrip(), percentage=args.percentage))