Run a Python script from another Python script passing in arguments

Question

I want to run a Python script from another Python script  I want to pass variables like I would using the command line   For example  I would run my first script that would iterate through a list of values  0 1 2 3  and pass those to the 2nd script script2 py 0 then script2 py 1  etc   I found Stack nbsp Overflow question 1186789 which is a similar question  but ars s answer calls a function  where as I want to run the whole script  not just a function  and balpha s answer calls the script but with no arguments  I changed this to something like the below as a test   execfile  script2 py 1     But it is not accepting variables properly  When I print out the sys argv in script2 py it is the original command call to first script    C  script1 py     I don t really want to change the original script  i e  script2 py in my example  since I don t own it   I figure there must be a way to do this  I am just confused how you do it

User · Answer

Ideally  the Python script you want to run will be set up with code like this near the end   def main arg1  arg2  etc         do whatever the script does   if   name         main         main sys argv 1   sys argv 2   sys argv 3     In other words  if the module is called from the command line  it parses the command line options and then calls another function  main    to do the actual work   The actual arguments will vary  and the parsing may be more involved    If you want to call such a script from another Python script  however  you can simply import it and call modulename main   directly  rather than going through the operating system   os system will work  but it is the roundabout  read  slow   way to do it  as you are starting a whole new Python interpreter process each time for no raisin

User · Answer

Try using os system   os system  script2 py 1     execfile is different because it is designed to run a sequence of Python statements in the current execution context  That s why sys argv didn t change for you

User · Answer

SubProcess module  http   docs python org dev library subprocess html using-the-subprocess-module  import subprocess subprocess Popen  script2 py 1   shell True    With this  you can also redirect stdin  stdout  and stderr

User · Answer

import subprocess subprocess call   python script2 py 1   shell True

User · Answer

This is inherently the wrong thing to do  If you are running a Python script from another Python script  you should communicate through Python instead of through the OS   import script1   In an ideal world  you will be able to call a function inside script1 directly   for i in range whatever       script1 some function i    If necessary  you can hack sys argv  There s a neat way of doing this using a context manager to ensure that you don t make any permanent changes   import contextlib  contextlib contextmanager def redirect argv num       sys  argv   sys argv        sys argv  str num       yield     sys argv   sys  argv  with redirect argv 1       print sys argv    I think this is preferable to passing all your data to the OS and back  that s just silly

User · Answer

I think the good practice may be something like this    import subprocess cmd    python script py   p   subprocess Popen cmd  stdout subprocess PIPE  shell True  out  err   p communicate    result   out split   n   for lin in result      if not lin startswith               print lin    according to documentation  The subprocess module allows you to spawn new processes  connect to their input output error pipes  and obtain their return codes  This module intends to replace several older modules and functions   os system os spawn  os popen  popen2   commands     Use communicate   rather than  stdin write   stdout read or  stderr read to avoid deadlocks due to any of the other OS pipe buffers filling up and blocking the child process  Read Here

[python] Run a Python script from another Python script, passing in arguments

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