Multithreaded Code explanation

Threading Module Introduction

The Multiprocess module completely imitates the interface of the threading module, which has a great similarity in the use level, so it is no longer described in detail

Website Link: https://docs.python.org/3/library/threading.html?highlight=threading#

Two ways to turn on multithreading

Method 1: Common

From threadingImportThreadDefTask ():Print‘is running‘)If__name__==‘__main__‘: T=thread (target=Task,) T.start ()#The overhead of opening a thread is small, the speed of the thread is open in the process, the thread is opened based on the current process spacePrint‘Main‘)‘‘‘Turn on the print result of a thread: print is running main‘‘‘From multiprocessingImportProcessDefTask ():print ( is Ruuing '  ' if __name__== ' 

Method 2: Not commonly used, some people use it.

From threadingImportThreadClassdefprint ( is Running ' ) if __name__== ' __main__ '  ' 

The difference between opening multiple threads under one process and opening multiple sub-processes under one process

 fromThreadingImportThreadclassMythread (Thread):defRun (self):Print('is running')if __name__=='__main__': T=Mythread () T.start ( )Print('Master')" "is running Master" " fromThreadingImportThread fromMultiprocessingImportProcessImportOSdeftask ():Print('%s is running'%os.getpid ())if __name__=='__main__': T1=thread (target=task,) T2= Thread (target=task,) T1.start () T2.start ( )Print('Master', Os.getpid ())" "#都是在同一个进程中1884 is running1884 is running main 1884" " fromThreadingImportThread fromMultiprocessingImportProcessImportOSdeftask ():Print('%s is running'%os.getpid ())if __name__=='__main__': P1=process (target=task,) P2= Process (target=task,) P1.start () P2.start ( )Print('Master', Os.getpid ())" "#主进程id和两个子进程id主 78166452 is running8436 running" "

PID

 fromThreadingImportThread fromMultiprocessingImportPROCESSN=100defWork ():GlobalN N=0if __name__=='__main__': P=process (target=Work ,) P.start () P.join ( )Print('Master', N)" "The main 100 found n is not modified because the main process is the program to run this file, the child process is P, only the process and child process space completely independent creation of the child process p, the child process copies the state of the parent process, including n=100, and then global n=0 The global variable of the child process is modified, and the printed n is the global variable of the parent process, so there is no change" " fromThreadingImportThread fromMultiprocessingImportPROCESSN=100defWork ():GlobalN N=0if __name__=='__main__': T=thread (target=Work ,) T.start ()Print('Master', N)" "Master 0 Discovery changes the space sharing between threads in the same process" "

name Space

Multithreaded Code explanation