def test():
    # n = 100
    #
    # sum = 0
    # counter = 1
    # while counter <= n:
    #     sum = sum + counter
    #     counter += 1
    # else:
    #     print("1 到 %d 之和为: %d" % (n, sum))

    # python 列表推导式
    #     格式 [表达式 for 变量 in 列表] 或者 [表达式 for 变量 in 列表 if 条件]
    #  out_exp_res: 列表生成元素的表达式，可以是有返回值的函数
    # for out_exp in input_list: 迭代input_list将out_exp传入到out_exp_res表达式中
    # if condition: 条件语句，可以过滤列表中不符合条件的值
    # names = ['Google', 'Runoob', 'Taobao']
    # names.append('Baidu')
    # new_names = [name.upper() for name in names if len(name) > 5]
    # print(new_names)
    #
    # multiples = [i for i in range(1, 30) if i % 3 == 0]
    # print(multiples)
    #
    # """
    # python 字段推导式
    # { key_expr: value_expr for value in collection}
    # 或
    # { key_expr: value_expr for value in collection if condition }
    # """
    # list_demo = ["Google", "Runoob", "Taobao"]
    # name_dict = {name: len(name) for name in list_demo}
    # print(name_dict)
    #
    #
    # dic = {x: x**2 for x in (2, 4, 6)}
    # print(dic)
    #
    # """
    # python 集合推导式
    # {expression for item}
    #
    #
    #
    # """

    # list = [1, 2, 3, 4, 5]
    # it = iter(list)  # 创建迭代器对象
    # print(next(it))  # 输出迭代器的下一个元素

    class MyNumbers:
        def __iter__(self):
            self.a = 1
            return self

        def __next__(self):
            x = self.a
            self.a += 1
            return x

    mycalss = MyNumbers()
    myiter = iter(mycalss)
    print(next(myiter))
    print(next(myiter))


if __name__ == '__main__':
    test()