Proper use of mutexes in Python

Question

I am starting with multi-threads in python  or at least it is possible that my script creates multiple threads   would this algorithm be the right usage of a Mutex  I haven t tested this code yet and it probably won t even work  I just want processData to run in a thread  one at time  and the main while loop to keep running  even if there is a thread in queue     from threading import Thread from win32event import CreateMutex mutex   CreateMutex None  False   My Crazy Mutex   while 1      t   Thread target self processData  args  some data        t start       mutex lock    def processData self  data      while 1          if mutex test      False              do some stuff             break   Edit  re-reading my code I can see that it is grossly wrong  but hey  that s why I am here asking for help

User · Answer

You have to unlock your Mutex at sometime

User · Answer

This is the solution I came up with    import time from threading import Thread from threading import Lock  def myfunc i  mutex       mutex acquire 1      time sleep 1      print  Thread   d   i     mutex release     mutex   Lock   for i in range 0 10       t   Thread target myfunc  args  i mutex       t start       print  main loop  d   i   Output   main loop 0 main loop 1 main loop 2 main loop 3 main loop 4 main loop 5 main loop 6 main loop 7 main loop 8 main loop 9 Thread  0 Thread  1 Thread  2 Thread  3 Thread  4 Thread  5 Thread  6 Thread  7 Thread  8 Thread  9

User · Answer

I would like to improve answer from chris-b a little bit more   See below for my code   from threading import Thread  Lock import threading mutex   Lock     def processData data  thread safe       if thread safe          mutex acquire       try          thread id   threading get ident           print   nProcessing data    data   ThreadId    thread id      finally          if thread safe              mutex release     counter   0 max run   100 thread safe   False while True      some data   counter             t   Thread target processData  args  some data  thread safe       t start       counter   counter   1     if counter  gt   max run          break   In your first run if you set thread safe   False in while loop  mutex will not be used  and threads will step over each others in print method as below     but  if you set thread safe   True and run it  you will see all the output comes perfectly fine     hope this helps

User · Answer

I don t know why you re using the Window s Mutex instead of Python s   Using the Python methods  this is pretty simple   from threading import Thread  Lock  mutex   Lock    def processData data       mutex acquire       try          print  Do some stuff       finally          mutex release    while True      t   Thread target   processData  args    some data        t start     But note  because of the architecture of CPython  namely the Global Interpreter Lock  you ll effectively only have one thread running at a time anyway--this is fine if a number of them are I O bound  although you ll want to release the lock as much as possible so the I O bound thread doesn t block other threads from running   An alternative  for Python 2 6 and later  is to use Python s multiprocessing package   It mirrors the threading package  but will create entirely new processes which can run simultaneously   It s trivial to update your example   from multiprocessing import Process  Lock  mutex   Lock    def processData data       with mutex          print  Do some stuff    if   name         main         while True          p   Process target   processData  args    some data            p start

[python] Proper use of mutexes in Python

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