Within Python 3.X, produces a random, alphanumeric string of desired length, with optional mixed case.

generate_alphanumeric_string.py

import string
import random
from functools import reduce

USABLE_SEQUENCE_WITH_LOWER = string.ascii_letters + string.digits
USABLE_SEQUENCE_WITHOUT_LOWER = string.ascii_uppercase + string.digits


def generate_secret(length=50, mixed_case=False):
    """
    Produces a random, alphanumeric string of a desired length.

    :param length: the length of the produced string.
    :param mixed_case: If True, the resulting string may have mixed-case.
    :return: A random, alphanumeric string of a desired length
    """

    if not isinstance(length, int):
        raise RuntimeError("length must be a number greater than 0")

    def inner_gen():
        for x in range(length):
            if mixed_case:
                yield random.choice(USABLE_SEQUENCE_WITH_LOWER)
            else:
                yield random.choice(USABLE_SEQUENCE_WITHOUT_LOWER)

    return reduce(lambda x, y: x + y, inner_gen(), "")


if __name__ == "__main__":
    print(generate_secret())