Make 2 functions run at the same time

Question

I am trying to make 2 functions run at the same time   def func1        print  Working   def func2        print  Working   func1   func2     Does anyone know how to do this

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test using APscheduler  from apscheduler schedulers background import BackgroundScheduler import datetime  dt   datetime datetime Future   dt now     datetime timedelta milliseconds 2550     2 55 seconds from now testing start accuracy  def myjob1        print  started job 1      str dt now     -3      timed to millisecond because thats where it varies     time sleep 5      print  job 1 half at      str dt now     -3       time sleep 5      print  job 1 done at      str dt now     -3   def myjob2        print  started job 2      str dt now     -3       time sleep 5      print  job 2 half at      str dt now     -3       time sleep 5      print  job 2 done at      str dt now     -3    print   current time      str dt now     -3   print    do job 1 at      str Future   -3           do job 2 at        str Future   -3   sched add job myjob1   date   run date Future  sched add job myjob2   date   run date Future   i got these results  which proves they are running at the same time   current time  2020-12-15 01 54 26 526   do job 1 at  2020-12-15 01 54 29 072    i figure these both say  072 because its 1 line of print code   do job 2 at  2020-12-15 01 54 29 072 started job 2  2020-12-15 01 54 29 075    notice job 2 started before job 1  but code calls job 1 first  started job 1  2020-12-15 01 54 29 076   job 2 half at  2020-12-15 01 54 34 077    halfway point on each job completed same time accurate to the millisecond job 1 half at  2020-12-15 01 54 34 077 job 1 done at  2020-12-15 01 54 39 078    job 1 finished first  making it  004 seconds faster  job 2 done at  2020-12-15 01 54 39 091    job 2 was  002 seconds faster the second test

User · Answer

I think what you are trying to convey can be achieved through multiprocessing  However if you want to do it through threads you can do this  This might help  from threading import Thread import time  def func1        print  Working      time sleep 2   def func2        print  Working      time sleep 2   th   Thread target func1  th start   th1 Thread target func2  th1 start

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Try this  from threading import Thread  def fun1        print  Working1   def fun2        print  Working2    t1   Thread target fun1  t2   Thread target fun2   t1 start   t2 start

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The thread module does work simultaneously unlike multiprocess  but the timing is a bit off  The code below prints a  quot 1 quot  and a  quot 2 quot   These are called by different functions respectively  I did notice that when printed to the console  they would have slightly different timings  from threading import Thread  def one        while 1    num           print  quot 1 quot           time sleep 2       def two        while 1    num           print  quot 2 quot           time sleep 2    p1   Thread target   one  p2   Thread target   two   p1 start   p2 start    Output   Note the space is for the wait in between printing  1 2  2 1  12     21  12     1 2  Not sure if there is a way to correct this  or if it matters at all  Just something I noticed

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The answer about threading is good  but you need to be a bit more specific about what you want to do   If you have two functions that both use a lot of CPU  threading  in CPython  will probably get you nowhere  Then you might want to have a look at the multiprocessing module or possibly you might want to use jython IronPython    If CPU-bound performance is the reason  you could even implement things in  non-threaded  C and get a much bigger speedup than doing two parallel things in python   Without more information  it isn t easy to come up with a good answer

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One option  that looks like it makes two functions run at the same time  is using the threading module  example in this answer    However  it has a small delay  as an Official Python Documentation page describes  A better module to try using is multiprocessing   Also  there s other Python modules that can be used for asynchronous execution  two pieces of code working at the same time   For some information about them and help to choose one  you can read this Stack Overflow question   Comment from another user about the threading module     He might want to know that because of the Global Interpreter Lock   they will not execute at the exact same time even if the machine in   question has multiple CPUs  wiki python org moin GlobalInterpreterLock       Jonas Elfstr  m Jun 2  10 at 11 39  Quote from the Documentation about threading module not working     CPython implementation detail  In CPython  due to the Global Interpreter   Lock  only one thread can execute Python code at once  even though   certain performance-oriented libraries might overcome this limitation        If you want your application to make better use of the computational resources of multi-core machines  you are advised to use multiprocessing or concurrent futures ProcessPoolExecutor    However  threading is still an appropriate model if you   want to run multiple I O-bound tasks simultaneously

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This can be done elegantly with Ray  a system that allows you to easily parallelize and distribute your Python code   To parallelize your example  you d need to define your functions with the  ray remote decorator  and then invoke them with  remote   import ray  ray init      Define functions you want to execute in parallel using    the ray remote decorator   ray remote def func1        print  Working     ray remote def func2        print  Working      Execute func1 and func2 in parallel  ray get  func1 remote    func2 remote       If func1   and func2   return results  you need to rewrite the above code a bit  by replacing ray get  func1 remote    func2 remote     with   ret id1   func1 remote   ret id2   func1 remote   ret1  ret2   ray get  ret id1  ret id2     There are a number of advantages of using Ray over the multiprocessing module or using multithreading  In particular  the same code will run on a single machine as well as on a cluster of machines    For more advantages of Ray see this related post

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Do this   from threading import Thread  def func1        print  Working    def func2        print  Working    if   name         main         Thread target   func1  start       Thread target   func2  start

[python] Make 2 functions run at the same time

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