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

python异常与生成器

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