yesno.py

def yesno(prompt, answers=None):
    if answers is None:
        answers = {
            'yes': True,
            'no': False
        }
    prompt = prompt.encode('ascii', 'ignore')

    while True:
        answer = raw_input(u'{0} [{1}]: '.format(
            prompt,
            u'/'.join(answers.keys())
        ))

        if answer in answers:
            return answers[answer]