python异常与生成器

列表生成器：

[ i*2 for i in range(10) ]这不是是生成器

[ func(i) for i in range(10) ]

( i*2 for i in range(10) ) 这就是生成器

 

一个算法，一个函数，可以边循环边生成数据，为了省空间，只有调用才会生成相应的数据。

只有__next()__方法

也可以用函数做个生成器

def fib(max):
    n,a,b = 0,0,1
    while n < max:
        print(b)
        a,b = b,a+b
        n = n + 1
    return 'done'
fib(10)


def fib(max):
    n,a,b = 0,0,1
    while n < max:
        yield(b)
        a,b = b,a+b
        n = n + 1
    return 'done'
print(fib(10))

fib_gen = fib(100)
print(fib_gen.__next__())
print(fib_gen.__next__())
print(fib_gen.__next__())

异常的捕获

def fib(max):
    n,a,b = 0,0,1
    while n < max:
        yield(b)
        a,b = b,a+b
        n = n + 1
    return 'done'
print(fib(10))

fib_gen = fib(10)
print(fib_gen.__next__())
print(fib_gen.__next__())
print(fib_gen.__next__())
print(fib_gen.__next__())
print(fib_gen.__next__())
print(fib_gen.__next__())
print(fib_gen.__next__())
print(fib_gen.__next__())
print(fib_gen.__next__())
while True:
    try:
        print(fib_gen.__next__())
    except StopIteration as e:
        print("Generator return value:",e.value)
        break

也可以这样

def fib(max):
n,a,b = 0,0,1
while n < max:
yield(b)
a,b = b,a+b
n = n + 1
return 'done'
print(fib(10))

fib_gen = fib(10)

while True:
try:
print(fib_gen.__next__())
except StopIteration as e:
print("Generator return value:",e.value)
break

 

生产者与消费者

import time
def consumer(name):
    print("%s准备吃包子"%name)
    while True:
        baozi = yield
        print("包子[%s]来了，被[%s]吃了！"%(baozi,name))

c = consumer("Roger")
c.__next__();
baozi = "肉包子"
c.send(baozi)

send唤醒generator且给yield发送指
__next()只是唤醒generator，走到yield处，中断，返回
继续
import time
def consumer(name):
    print("%s准备吃包子"%name)
    while True:
        baozi = yield
        print("包子[%s]来了，被[%s]吃了！"%(baozi,name))

c = consumer("Roger")
c.__next__();
baozi = "肉包子"
c.send(baozi)
def producer(name):
    c = consumer('A')
    c2 = consumer('B')
    c.__next__()
    c2.__next__()
    print("我开始准备做包子啦")
    for i in range(10):
        time.sleep(1)
        print("做了2个包子")
        c.send(i)
        c2.send(i)
producer("alex")

生成器可以实现，单线程下的并行效果

携程