Smth wrong.

I enter my code, push "Run&Checl" and start waiting: Loading...(29) And nothing. Code:

def checkio(data):
    if len(data)<10:
        return False
    else:
        passworD_full=0
        passworD_high=str.upper(data)
        passworD_low=str.lower(data)
        numbers=str("0123456789")
        u=0
        if str.isdigit(data) is False:
            answer_digits=True
            while u<=len(numbers):
                for o in numbers:
                    for x in data:
                        if o==x:
                            answer_numbers=True
                            u=len(numbers)
                        else:
                            u+=1
            if answer_numbers==True:
                if passworD_high!=data:
                    if passworD_low!=data:
                        return True
                    else:
                        return False
                else:
                    return False
            else:
                return False
        else:
            return False

As you can see, I'm a newbie :)