python学习（14）- 生成器

超、凢脫俗 2022-12-28 11:13 195阅读 0赞

Python学习（13）- 三大式

[https://blog.csdn.net/caoyan0829/article/details/111252490][https_blog.csdn.net_caoyan0829_article_details_111252490]

生成器：

"""
    GeneratorExit
    generator
    生成器：一边循环一边计算来生成想要的数字
    """
    l = [i for i in range(20) if i % 2 == 0]
    print(l)  # [0, 2, 4, 6, 8, 10, 12, 14, 16, 18]
    
    g = (i for i in range(20) if i % 2 == 0)
    print(g)  # <generator object <genexpr> at 0x0000021DAE417040>
    
    print(next(g))  # 0
    print(g.__next__())  # 2
    print(next(g))  # 4
    
    l1 = []  # 取三个
    for i in range(3):
        l1.append(next(g))
    print(l1)
    
    """
    2. yield在函数中，这个函数就是生成器，不是函数
        可以相当于return 但是还可以往下走
    
        函数是顺序执行，遇到return语句或者最后一行函数语句就返回。
        而变成generator的函数，在每次调用next()的时候执行，
        遇到yield语句返回，再次执行时从上次返回的yield语句处继续执行。
    """
    
    
    def gen():
        for i in range(10):
            print(i)
        yield '哈哈'
    
    
    print(gen())  # <generator object gen at 0x0000014FF0E98890>
    
    
    def gen1():
        i = 0
        while i < 5:
            yield i  # 执行到这停止，光标记录位置，下次从这开始
            i += 1
    
    
    g1 = gen1()
    print(next(g1))  # 0
    print(next(g1))  # 1
    print(next(g1))  # 2
    print(next(g1))  # 3
    
    """
    temp 是send传过来的值
    """
    
    
    def gen2():
        i = 0
        while i < 5:
            temp = yield i  # 可通过send()传值
            print(temp, end=' ')
            i += 1
    
    
    g2 = gen2()
    print(next(g2))  # 0
    print(next(g2))  # None 1
    g2.send('测试')
    print(next(g2))  # 测试 None 3
    print(next(g2))  # None 4
    
    """
    斐波那契数列 
    1 1 2 3 5 8 13 21 34 。。。
    """
    def fib(num):
        i, a, b = 0, 0, 1
        while i < num:
            yield b
            a, b = b, a + b
            i += 1
    g = fib(10)
    
    for i in g:
        print(i) 
    
    print(next(g)) #1
    print(next(g)) #1
    print(next(g)) #2
    print(next(g)) #3
    print(next(g)) #5
    print(next(g)) #8
    print(next(g)) #13

python学习（15）- 迭代器

[https://blog.csdn.net/caoyan0829/article/details/111296781][https_blog.csdn.net_caoyan0829_article_details_111296781]

[https_blog.csdn.net_caoyan0829_article_details_111252490]: https://blog.csdn.net/caoyan0829/article/details/111252490
[https_blog.csdn.net_caoyan0829_article_details_111296781]: https://blog.csdn.net/caoyan0829/article/details/111296781