import string
import random


def random_string_generator(size=10, chars=string.ascii_lowercase + string.digits):
    """
    Generates and returns a random string of given size.

    :size: Size of the desired random string. Default is 10
    :type size: int
    :param chars: Characters from which random string is to be generated.
        Default value is `abcdefghijklmnopqrstuvwxyz0123456789`
    :type chars: str
    :returns: A random string.
    :rtype: str
    """

    return ''.join(random.choice(chars) for _ in range(size))