python 生成器generator

１．使用（）
a=[x for x in range(10)]
print(type(a)) #list
print(isinstance(a,Iterator)) #false

b=(i for i in range(1000000000000000000000000))#cpu不会卡死
print(type(b)) #generator
print(isinstance(b,Iterator)) #true
while True:
    try:
        print(next(b))
    except Exception as e:
        print(e)
２．使用yield,
next会催动程序从yield运行到取出下一个yield的值返回(卡在这)

def fib():
    a=1
    b=1
    n=0
    while True:
        a,b=b,a+b
        yield b
f=fib()  #创建生成器
for i in f: #此处相当于next(f)
    print(i)



send传值＋next:

def f():
    for i in range(10000000000000000000):
        if i%2==0:
            r=yield i
            print('这是第 %s个'% r)

f=f()
print(next(f))
print(f.send('1')) 
print(f.send('2'))
print(f.send('3'))