Python learns day14 processes and threads

    Process

#********* Creating a single process through process fromMultiprocessingImportProcessImportOS#code to be executed by the child processdefRun_proc (name):Print('Run Child process%s (%s) ...'% (name, Os.getpid ()))#gets the name of the current process, the PID valueif __name__=='__main__':    Print('Parent process%s.'%os.getpid ()) P= Process (Target=run_proc, args= ('Test',))#the name of the function passing in the child process, giving the child process a name    Print('Child process would start.') P.start () P.join ()Print('Child process end.')#Parent process 9976.#Child process would start.#Run Child Process Test (9368) ...#Child process end.#************* creates multiple processes through the pool, with parameters within the pool being the maximum number of concurrently executing processes fromMultiprocessingImportPoolImportOS, time, RandomdefLong_time_task (name):Print('Run Task%s (%s) ...'%(name, Os.getpid ())) Start=time.time () time.sleep (Random.random ()* 3) End=time.time ()Print('Task%s runs%0.2f seconds.'% (name, (End-start )))if __name__=='__main__':    Print('Parent process%s.'%os.getpid ()) P= Pool (4)     forIinchRange (5): P.apply_async (long_time_task, args=(i,))Print('waiting-subprocesses done ...') P.close () P.join ()Print('All subprocesses is done .')#Parent process 8808.#waiting-subprocesses done ...#Run Task 0 (2956) ...#Run Task 1 (5296) ...#Run Task 2 (8432) ...#Run Task 3 (8412) ...#Task 3 runs 0.10 seconds.#Run Task 4 (8412) ...#Task 2 runs 0.41 seconds.#Task 4 runs 1.61 seconds.#Task 1 runs 1.90 seconds.#Task 0 runs 2.09 seconds.#All subprocesses is done .#****************** subprocess can let us start a child process conveniently, and then control its input and output, Nslookup is a command under the terminal, can find the IP of the specified URLImportsubprocessPrint('$ nslookup www.python.org') R= Subprocess.call (['nslookup','www.python.org'])#A child process was created and Nslookup www.python.org was enteredPrint('Exit Code:', R)" "" "#************** If the child process also needs input, you can enter it through the communicate () methodImportsubprocessPrint('$ nslookup') P= subprocess. Popen (['nslookup'], stdin=subprocess. PIPE, Stdout=subprocess. PIPE, stderr=subprocess. PIPE) output, err= P.communicate (b'Set q=mx\npython.org\nexit\n')Print(Output.decode ('GBK'))#Print (Output.decode (' utf-8 ')) source code is utf-8 but will error, look at the comments below is the coding problem, change to GBK is good#because pycharm default is Utf-8, which also leads to the above example is garbled, ' $ nslookup www.baidu.com ' equivalent to the command run in cmd, the command is displayed after the result is also cmd results, \#and the cmd itself default encoding is GBK, so there will be garbled. Workaround: File>>settings>>file encodings>>project Encoding: (select GBK)Print('Exit Code:', P.returncode)#The above code is equivalent to executing command nslookup at the command line, and then manually entering:#Set Q=MX#python.org#Exit#The output is as follows#$ nslookup#server:192.168.19.4#address:192.168.19.4#53# #non-authoritative Answer:#python.org Mail exchanger = mail.python.org.# #authoritative answers can found from:#mail.python.org Internet address = 82.94.164.166#mail.python.org has AAAA address 2001:888:2000:d::a6# # #Exit code:0#************* inter-process communication fromMultiprocessingImportProcess, QueueImportOS, time, Random#code to write the data Process execution:defWrite (q):Print('Process to write:%s'%os.getpid ()) forValueinch['A','B','C']:        Print('Put%s to queue ...'%value) q.put (value) time.sleep (Random.random ())#read the code that the data process executes:defRead (q):#Incoming queue () queues through Q so you can save the data.    Print('Process to read:%s'%os.getpid ()) whileTrue:value= Q.get (True)#the True here is actually a parameter (block=true), which means that it is blocked when there is no data in the queue        Print('Get%s from queue.'%value)if __name__=='__main__':    #The parent process creates a queue and passes it to each child process:Q =Queue () PW= Process (Target=write, args=(q,)) PR= Process (Target=read, args=(q,))#Start child process PW, write:Pw.start ()#start child process PR, read:Pr.start ()#wait for PW to end:Pw.join ()#PR process is a dead loop, can not wait for its end, can only forcibly terminate:Pr.terminate ()

Python learns day14 processes and threads