Can I make a session on os.system

[Serferi]

There is my code, he work with python 2.7 on linux

         
         print "OUI"
         os.system("python ../updater.3.pyc")
         os.system("cd .. | pwd")
         path = "../../.."
         files = os.listdir(path)
         listeFichiers = []
         for (repertoire, sousRepertoires, fichiers) in walk(path):
             for fichiers2 in fichiers:
                 if u'.cap.' in fichiers2:
                     #//////These commande must be make after the update
                     listeFichiers.append(fichiers2)
                     avant = fichiers2.replace(".cap", "")
                     shutil.copyfile(repertoire + "/" + avant,repertoire + "/" + fichiers2.replace(".cap", ".old") )
                     shutil.copyfile(repertoire + "/" + fichiers2, repertoire + "/" + avant)
         

My script have to make an update and after that change png icon, but the problem is that my script don't wait the end of the update and change
the icon befor. Second problem, I can't make a sleep because the time of the update can change.

So my question is : How can I make a session of os.system for be sure that my script wait the end of the update.

[woooee]

The program should wait for the os.system to finish before executing other statements. Two other options, 1) use subprocess.run
https://pymotw.com/3/subprocess/index.html 2) import the 2nd program and call a function or class within that program