• day 13 生成器,推导式


    1. 生成器和生成器函数

      生成器的本质就是迭代器

      生成器的三种创建办法:
        1.通过生成器函数

        2.通过生成器表达式创建生成器

        3.通过数据转换

    # def func():
    #     print("我是周杰伦")
    #     yield "昆凌"  # 函数中包含了yield, 当前这个函数就不再是普通的函数了. 是生成器函数
    #     print("我是王力宏")
    #     yield "李云迪???"
    #     print("我是笛卡尔积")
    #     yield "笛卡尔积是谁"
        # print("你好啊") # 最后一个yield之后如果再进行__next__() 会报错
    # g = func()
    # print(g.__next__())
    # print(func().__next__())
    #
    # g1 = func()
    # g2 = func()
    # print(g1.__next__())
    # print(g1.__next__())
    #
    # print("==============")
    # print(g2.__next__())

    生成器函数:

      函数中包含了yield的就是生成器函数

      注意:生成器函数被执行. 获取到的是生成器. 而不是函数的执行

    生成器表达式:

      (结果 for 变量 in 可迭代对象 if 筛选)

    取值:

      1. __next__()

      2. send(值) 给上一个yield位置传一个值, 第一个和最后一个yield不用传值

      3. 可以for循环

      4. list(g)

    # g = func()  # 通过函数func()来创建一个生成器
    # print(g.__next__()) # 周杰伦
    # print(g.__next__()) # 王力宏
    # print(g.__next__()) # 笛卡尔积
    # print(g.__next__())
    
    # return 直接返回结果. 结束函数的调用
    # yield 返回结果.可以让函数分段执行
    #
    # def func():
    #     lst = []
    #     for i in range(1,100001):
    #         lst.append("衣服%s" % i)
    #     return lst
    #
    # def gen():
    #     i = 1
    #     while i < 100001:
    #         yield "衣服%s" % i
    #         i = i + 1
    # g = gen()
    # print(g.__next__())
    # print(g.__next__())
    # print(g.__next__())
    # print(g.__next__())
    # print(g.__next__())
    # print(g.__next__())
    
    #
    # def func():
    #     yield 11
    #     yield 22
    #     yield 33
    #     yield 44
    # g = func()  # 拿到的是生成器. 生成器的本质是迭代器. 迭代器可以被迭代 生成器可以直接for循环
    #
    # for i in g:
    #     print(i)    # 本质上执行的是__next__()
    #
    # it = g.__iter__()
    # while True:
    #     try:
    #         print(it.__next__())
    #     except StopIteration:
    #         break

    2. 各种推倒式和生成器表达式

      1. 列表推倒式 [结果 for 变量 in 可迭代对象 if 筛选]

    # 生成列表 里面装1-14的数据
    # lst = []
    # for i in range(1,15):
    #     lst.append("python%s" % i)
    # print(lst)
    
    # 列表推倒式; 最终给你的是列表
    # 语法 [最终结果(变量) for 变量 in 可迭代对象]
    
    # lst = [i for i in range(1,15)]
    # print(lst)
    
    # [最终结果 for 变量 in 可迭代对象 if 条件]
    lst = [i for i in range(1,101) if i%2==0]
    print(lst)
    
    # 1. 获取1-100内能被3整除的数
    # lst = [i for i in range(1,101) if i % 3 == 0]
    # 2. 100以内能被3整除的数的平方
    # lst = [i*i for i in range(1,101) if i % 3 == 0]
    # 3. 寻找名字中带有两个e的⼈的名字
    # names = [['Tom', 'Billy', 'Jefferson' , 'Andrew' , 'Wesley' , 'Steven' ,
    # 'Joe'],['Alice', 'Jill' , 'Ana', 'Wendy', 'Jennifer', 'Sherry' , 'Eva']]
    # lst = [name for first in names for name in first if name.count("e") == 2]
    # print(lst)
    #
    # lst = ["衣服%s" % i for i in range(10000)]

      2. 字典推倒式 {结果 for 变量 in 可迭代对象 if 筛选} 结果=>key:value

    # g = (i for i in range(10))
    # print(list(g))
    
    # gen = ("麻花藤我第%s次爱你" % i for i in  range(10))
    # for i in  gen:
    #     print(i)
    
    # 生成器的惰性机制
    # def func():
    #     print(111)
    #     yield  222
    # g = func()
    # g1 = (i  for i in  g)
    # g2 = (i  for i in  g1)
    #
    # print(list(g))
    # print(list(g1))
    # print(list(g2))
    # dic = {"a":"b", "c":"d"}
    # # 把字典中的key:value互换 .{"b":"a", "d":"c"}
    # new_dic = {dic[key]:key for key in dic}
    # print(new_dic)
    
    # lst1 = ["alex", "wusir", "taibai", "ritian"]
    # lst2 = ['sb', "很色", "很白", "很牛"]
    # # {"alex":"sb", "wusir":"很色"}
    #
    # dic = { lst1[i]:lst2[i] for i in range(len(lst1))}
    # print(dic)
    
    
    
    # dic = {"a":"b","c":"d"}
    # #把字典中的key:value互换.{"b":"a":"d":"c"}
    # new_dic = {dic[key]:key for key in dic}
    # print(new_dic)
    #
    # #lst1 = ["alex","wusir","taibai","ritian"]
    # #lst2 = ['sb',"很色","很白","很牛"]
    # #{"alex":"sb","wusir":"很色"}
    # dic = {lst1[1]:lst2[i] for i in range(len(lst1))}
    # print(dic)
    #
    # dic = {"a":"b","c":"d"}
    
    
    # name = "aleX leNb"
    # e1 = name.find("e", 0,5)
    # print(e1)
    #
    # e2 = name.find("e",5)
    # print(e2)
    
    # count = 1
    # while count <= len(name):
    #     if name[count] =='e':
    #         print(count)
    #     count = count + 1
    #
    # s = "123a4b5c"
    # s = "asdfer"
    # for c in s:     #c :chartor
    #     print(c)
    
    # content = input("请输入内容")
    # lst = content.split("+")
    # s1 = lst[0]
    # s2 = lst[1]
    # a1 = int(s1)
    # a2 = int(s2)
    # print(a1+a2)
    #
    # lst = ["皇阿玛", "皇额娘", "容嬷嬷", "紫薇"]
    # it = lst.__iter__()
    # while True:
    #     try:
    #         name = it.__next__()
    #         print(name)
    #     except StopIteration:
    #         break
    #
    #
    # dic = {"a":"b", "c":"d"}
    # new_dic = {dic[key]:key for key in dic}  #字典的key和value对调
    # print(new_dic)
    #
    #
    # lst1 = ["alex","wusir","taibai","ritian"]
    # lst2 = ['sb',"很色","很白","很牛"]
    # dic = {lst1[i]:lst2[i] for i in range(len(lst1))}
    # print(dic)
    # #列表1和列表二合并,1作为key,2作为value
    
    
    
    # def func():
    #     print("111")
    #     return 222
    # ret = func()
    # print(ret)
    
    
    # def func():
    #     print("111")
    #     yield 222
    # ret = func()
    # print(ret)
    
    
    
    g = (i for i in range(10))
    print(list(g))

      3. 集合推倒式 {结果 for 变量 in 可迭代对象 if 筛选} 结果=>key

    lst = ["马化腾", "马化腾", "王建忠", "张建忠", "张建忠", "张雪峰", "张雪峰"]
    
    s = {i for i in lst}    # 集合推倒式
    print(s)
    def add(a, b):
        return a + b
    def test():
        for i in range(4):
            yield i
    g = test()
    def func():
        name = "alex"
        def inner():
            print(name)
        inner()
        print(inner.__closure__)
    func()

      

    def add(a, b):
        return a + b
    
    
    def gen():
        for r_i in range(4):
             yield r_i
    
    
    g = gen()
    
    for n in [2, 10]:
        g = (add(n, i) for i in g)
    print(list(g))
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  • 原文地址:https://www.cnblogs.com/songhuasheng/p/9470471.html
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