import random


class PasswordGenerator:    
    def __init__(self, length, count, charset = list("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789")):

        if count < 0:
            raise ValueError("Count must be non-negative")
        if length < 0:
            raise ValueError("Length must be non-negative")
        if not charset:
            raise ValueError("Charset must not be empty")

        self.length = length
        self.count = count
        self.charset = charset

    def __iter__(self):
        return self

    def __next__(self):
        if self.count == 0:
            raise StopIteration
        self.count -= 1
        return "".join(random.choices(self.charset, k=self.length))


if __name__ == "__main__":
    generator = PasswordGenerator(10, count=10)

    print("for loop")
    for password in generator:
        print(password)

    print()

    print("charset = 1234")
    generator = PasswordGenerator(10, count=3, charset=list("1234"))
    for password in generator:
        print(password)

    print()
    generator = PasswordGenerator(10, count=2)
    print("__next__(), generator count = 2")

    print(generator.__next__())
    print(generator.__next__())
    

    print("what happens when you call __next__ too many times:")
    # exception            # b

    print(generator.__next__())