python coroutine

目录

• python coroutine
  • 前言
  • Coroutines
  • Reference

python coroutine

前言

OOAD课程是用python教的，其中涉及到大量的python语法糖，老师也算是手把手教如何写出OO的python，但一个学期没听课只能期末补一补。

Coroutines

Coroutines are similar to generators with a few differences. The main differences are:

• generators are data producers generators制造数据
• coroutines are data consumers coroutines消费数据

来看第一个代码示例，通过send（）接收数据，然后进行比对，找出含有关键字的数据并打印。

def grep(pattern):
    print("Searching for", pattern)
    while True:
        line = (yield)
        if pattern in line:
            print(line)


search = grep('coroutine')
next(search)
# Output: Searching for coroutine
search.send("I love you")
search.send("Don't you love me?")
search.send("I love coroutines instead!")

很明显我们可以看到，yield关键字在这里已经从返回数据的变为接收数据的。也就是，Python的yield不但可以返回一个值，它还可以接收调用者发出的参数。

---

在中文里，coroutine对应的是协程，但是显然老师的重点不是什么同步异步，而是yield，以及coroutine和subprogram的区别。

Subprogram vs Coroutine, is (programming) a piece of code that performs a task, and that can be passed new input and return output more than once. As nouns the difference between subroutine and coroutine is that subroutine is (computer science) a section of code, called by the main body of a program, that implements a task while coroutine is (programming) a piece of code that performs a task, and that can be passed new input and return output more than once.

放上老师PPT的测试代码就收工：

def coroutine(y):
    for i in range(y):
        x = yield i
        print("i=%d , x=%d " % (i, x))


c = coroutine(4)
next(c)  
c.send(10) 
c.send(20)
c.send(30)

def echo():
    just_received='nothing'
    try:
        while True:
            received=yield just_received
            just_received=received
            print('I got {}.'.format(just_received))
    except GeneratorExit:
        # when closed with close()
        print('Coroutine closed!')


g = echo()
next(g)
g.send('test1')
g.send('test2')
g.close()

Reference

https://book.pythontips.com/en/latest/coroutines.html

http://lanlab.org/course/2019f/oo/OOLectureNotes.pdf

https://www.xspdf.com/resolution/50035685.html