Python Learning Notes-co-process

Python controls concurrency, In addition to multithreading and multi-process, you can also use the CO-COROUTINE. He switches from one thread to another through the Programmer's human Designation.

Example 1: a switch () can be used to move the person back and forth to another function; when all functions are finished, the final output print (10)

#!/usr/bin/env python#-*-coding:utf-8-*-# author:alex lifrom greenlet import greenletdef test1 (): print (+) gr2.s Witch () Print (gr2.switch) print (' 9 ') def test2 (): print (gr1.switch) () print (+) gr1.switch () gr 1 = greenlet (test1) GR2 = Greenlet (test2) gr1.switch () Print (ten)--------12563478910

Example 2, in addition to the Greenlet module we can also use the Gevent module

Gevent is a third-party library, through the Greenlet implementation of the process, the basic idea is:

When an greenlet encounters an IO operation, such as accessing the network, it automatically switches to the other greenlet, waits until the IO operation is complete, and then switches back to execution at the appropriate Time. Because the IO operation is very time-consuming and often puts the program in a waiting state, with gevent automatically switching the co-process for us, it is guaranteed that there will always be greenlet running, rather than waiting for io.

Since the switchover is done automatically during IO operations, gevent needs to modify some of the standard libraries that Python comes with, which is done at startup with Monkey Patch:

For example: first import gevent and Monkey patches, then define a function f, Gevent.spawn's main function is to produce greenlet objects, then he will automatically switch internally, when the first print command is executed, because it will block, it will automatically switch to other Greenlet objects to perform the operation, and then switch back to get the data results.

#!/usr/bin/env python# -*- coding:utf-8 -*-from gevent import monkey;  Monkey.patch_all () import geventimport requestsdef f (url):     print (' GET:  %s '  % url)     resp = requests.get (url)      Data = resp.text    print ('%d bytes received from %s. '   %  (len (data),  url)) gevent.joinall ([        gevent.spawn (f,   ' https://www.python.org/'),         gevent.spawn (f,  ' https:/ /www.yahoo.com/'),         gevent.spawn (f,  ' https://github.com/'), ])----------"c:\program files\python3\python.exe"  c:/temp/s13day11/day11/s18.pyget: https:// Www.python.org/GET: https://www.yahoo.com/GET: https://github.com/47413 bytes received  from https://www.python.org/.24810 bytes received from https://github.com/.450576 bytes  received from https://www.yahoo.com/.

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Python Learning Notes-co-process