python異常與產生器

標籤：喚醒   func   print   font   while   ret   bsp   time   消費   

清單產生器：

[ i*2 for i in range(10) ]這不是是產生器

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

( i*2 for i in range(10) ) 這就是產生器

 

一個演算法，一個函數，可以邊迴圈邊產生資料，為了省空間，只有調用才會產生相應的資料。

只有__next()__方法

也可以用函數做個產生器

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__())

異常的捕獲

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

也可以這樣

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

 

生產者與消費者

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

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

send喚醒generator且給yield發送指
__next()只是喚醒generator，走到yield處，中斷，返回
繼續
import time
def consumer(name):
    print("%s準備吃包子"%name)
    while True:
        baozi = yield
        print("包子[%s]來了，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("我開始準備做包子啦")
    for i in range(10):
        time.sleep(1)
        print("做了2個包子")
        c.send(i)
        c2.send(i)
producer("alex")

產生器可以實現，單線程下的並行效果

攜程

 

 

　　

 

python異常與產生器