python生成指定长度的随机字符串

from random import Randomdef random_str(randomlength=8):    str = ''    chars = 'AaBbCcDdEeFfGgHhIiJjKkLlMmNnOoPpQqRrSsTtUuVvWwXxYyZz0123456789'    length = len(chars) - 1    random = Random()    for i in range(randomlength):        str+=chars[random.randint(0, length)]    return str