python 生成随机字符串

import string
import time
import random

def create_name(prefix="", length=8, allnum=False, allalpha=False, time_subfix=False, onlylow=True):
    """
    创建随机字符串，仅包含大小写字母、数字
    :param prefix: 前缀，默认无
    :param length: 字符串长度
    :return: 返回创建的字符串
    """
    prefix_len = 0
    if prefix:
        prefix_len = len(prefix)
        try:
            assert prefix_len < length
        except:
            return prefix
    name_len = length - prefix_len
    temp_str = string.ascii_letters
    temp_num = string.digits
    if allnum and allalpha:
        raise ValueError('allnum和allalpha不能同时为True')
    elif allnum:
        new_name = prefix + ''.join([random.choice(temp_num) for i in range(name_len)])
    elif allalpha:
        new_name = prefix + ''.join([random.choice(temp_str) for i in range(name_len)])
    else:
        new_name = prefix + "".join([random.choice(temp_str + temp_num) for i in range(name_len)])
    if time_subfix:
        new_name += str(int(time.time()))
    print("create new name: %s" % new_name)
    if onlylow:
        new_name = new_name.lower()
    return new_name