Using a Python subprocess call to invoke a Python script

Question

I have a Python script that needs to invoke another Python script in the same directory. I did this:

from subprocess import call call('somescript.py') 

I get the following error:

call('somescript.py') File "/usr/lib/python2.6/subprocess.py", line 480, in call return Popen(*popenargs, **kwargs).wait() File "/usr/lib/python2.6/subprocess.py", line 633, in __init__ errread, errwrite) File "/usr/lib/python2.6/subprocess.py", line 1139, in _execute_child  raise child_exception OSError: [Errno 2] No such file or directory 

I have the script somescript.py in the same folder though. Am I missing something here?

Answer 1

If 'somescript.py' isn't something you could normally execute directly from the command line (I.e., $: somescript.py works), then you can't call it directly using call.

Remember that the way Popen works is that the first argument is the program that it executes, and the rest are the arguments passed to that program. In this case, the program is actually python, not your script. So the following will work as you expect:

subprocess.call(['python', 'somescript.py', somescript_arg1, somescript_val1,...]). 

This correctly calls the Python interpreter and tells it to execute your script with the given arguments.

Note that this is different from the above suggestion:

subprocess.call(['python somescript.py']) 

That will try to execute the program called python somscript.py, which clearly doesn't exist.

call('python somescript.py', shell=True) 

Will also work, but using strings as input to call is not cross platform, is dangerous if you aren't the one building the string, and should generally be avoided if at all possible.