import re


def containsAlphaNumeric(a_string):
    """Assumes a_string is a string
    returns a boolean, True if a_string contains only alphanumeric characters
    (a-z, A-Z and 0-9), else False
    """
    regex = "[a-zA-z0-9]+"
    results = re.search(regex, a_string)
    return bool(results)