生成器

生成器   

只要有yield就是生成器函数, yield有返回值,和记录执行到哪里,只能向下执行

函数名+()生成一个生成器  g=foo()

foo().__next__触发启动这个生成器

__next__和yield要一一对应,最后一个yield下边能写不运行

def foo():
    print(1)
    yield 4
    print(2)
    yield 7
g=foo()
print(g.__next__())
print(g.__next__())

好处:节省空间

def gen():
    for i in range(2000):
        yield i
g=gen()
for i in range(10):
    print(g.__next__())

send()=__next__+传值

def func():
    print(44)
    l=yield 5
    print(l)
    yield 66
g=func()
print(g.__next__())
print(g.send('黄瓜味脉动'))

 yield from lst

def foo():
    lst=[1,2,3,4]
    yield from lst
g=foo()
print(g.__next__())
print(g.__next__())
print(g.__next__())
print(g.__next__())

推导式

列表推导式
print([i for i in range(10)])
print([i for i in range (10) if i%2] )

集合推导式
dic={'1':2,'2':3}
d={i for i in dic.items()}

字典推导式
lst1=['1','2']
lst2=[2,3]
d={lst1[i]:lst2[i] for i in range(2)}

生成器导式
l=(i for i in range(100))
for i in range(10):
    print(l.__next__())