What s the difference between subprocess Popen and call how can I use them

Question

I want to call an external program from Python  I have used both Popen   and call   to do that    What s the difference between the two   My specific goal is to run the following command from Python  I am not sure how redirects work     my script sh  gt  output   I read the documentation and it says that call   is a convenience function or a shortcut function  Do we lose any power by using call   instead of Popen

User · Answer

The other answer is very complete  but here is a rule of thumb    call is blocking   call  notepad exe   print  hello      only executed when notepad is closed  Popen is non-blocking   Popen  notepad exe   print  hello      immediately executed

User · Answer

There are two ways to do the redirect  Both apply to either subprocess Popen or subprocess call    Set the keyword argument shell   True or executable    path to the shell and specify the command just as you have it there  Since you re just redirecting the output to a file  set the keyword argument  stdout   an open writeable file object   where the object points to the output file    subprocess Popen is more general than subprocess call   Popen doesn t block  allowing you to interact with the process while it s running  or continue with other things in your Python program  The call to Popen returns a Popen object   call does block  While it supports all the same arguments as the Popen constructor  so you can still set the process  output  environmental variables  etc   your script waits for the program to complete  and call returns a code representing the process  exit status    returncode   call  args    kwargs     is basically the same as calling   returncode   Popen  args    kwargs  wait     call is just a convenience function  It s implementation in CPython is in subprocess py   def call  popenargs  timeout None    kwargs          Run command with arguments   Wait for command to complete or     timeout  then return the returncode attribute       The arguments are the same as for the Popen constructor   Example       retcode   call   ls    -l                with Popen  popenargs    kwargs  as p          try              return p wait timeout timeout          except              p kill               p wait               raise   As you can see  it s a thin wrapper around Popen

[python] What's the difference between subprocess Popen and call (how can I use them)?

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