#随机生成字符串    
    def random_str(self, num):
        str = ''
        chars = 'AaBbCcDdEeFfGgHhIiJjKkLlMmNnOoPpQqRrSsTtUuVvWwXxYyZz0123456789-_'
        length = len(chars) - 1
        for i in range(num):
            str +=chars[random.randint(0, length)]
        return str
    #随机生成数字字符串
     def random_int(self, num):
        str = ''
        chars = '0123456789'
        length = len(chars) - 1
        for i in range(num):
            str +=chars[random.randint(0, length)]
        return int(str)
    #随机生成数字字符串+字母字符串
    def random_rid(self, num=15):
        str = ''
        chars = '0123456789'
        chars1 = 'AaBbCcDdEeFfGgHhIiJjKkLlMmNnOoPpQqRrSsTtUuVvWwXxYyZz0123456789'
        length = len(chars) - 1
        length1 = len(chars1) - 1
        for i in range(5):
            str +=chars[random.randint(0, length)]
        for i in range(num):
            str +=chars1[random.randint(0, length1)]
        return str

　　记录经常使用的一些方法，不用每次都自己写