How to use pathlib along with subprocess

Question

I would like to use relative paths along with subprocess module in order to be able to run different executables.

For getting relative paths and, after reading different threads, I think pathlib module is the best option to do that.

Let assume I have the python script in a particular folder in Windows. Inside it (the previous folder), I have other folders with the executables I want to run. Here it is when subprocess module comes in. However, I do not know how to include the relative paths created with pathlib module into subprocess args field.

From subprocess API I can read that 'args should be a sequence of program arguments or else a single string'.

import pathlib
import subprocess

in_file_1 = pathlib.Path.cwd() / "folder2" / "folder3" / "whatever.exe"

p = subprocess.Popen(str(in_file_1), shell = True)

I would expect to see the whatever.exe process running on the administrator tasks but the process is not started. How can I achieve that? Is there something I am ingoring? Should I just give the relative path from where the python script is saved?

I just tested your snippet and everything works as expected. Are you sure about your whatever.exe location? Why do you want to use the current working dir? — nicoco
– nicoco, Commented Jan 30, 2019 at 10:32
Yes, I am sure about the whatever.exe location. If I save the python script in the same folder as the whatever.exe the above code works but If I save it upstream whatever.exe does not work even specifying the relative path to it. — FJSJ
– FJSJ, Commented Jan 30, 2019 at 11:32
You are using pathlib.Path.cwd() so what matters is the current dir when you launch the script, not where the script is located. — nicoco
– nicoco, Commented Jan 30, 2019 at 11:53
That is what I am trying to do with ´in_file_1´ in order to obtain the current location of the python script. But even with that, I cannot make it work. Thank you for your comments @nicoco — FJSJ
– FJSJ, Commented Jan 30, 2019 at 12:06

nicoco · Accepted Answer · 2019-01-30 13:43:41Z

4

You are confusing the current working directory, which is what pathlib.Path.cwd() returns, with the script's location.

If you want the script's dir, you can use __file__, for instance like this:

import pathlib

cwd = pathlib.Path.cwd()
script_file = pathlib.Path(__file__)
script_location = script_file.parent

print("The current dir is", pathlib.Path.cwd())
print("The current script is", script_file)
print("The current script's dir is", script_file.parent)

which will return:

The current dir is /home/nicoco
The current script is /tmp/so.py
The current script's dir is /tmp

answered Jan 30, 2019 at 13:43

nicoco

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1 Comment

FJSJ Over a year ago

Thank you for your help @nicoco. Now it is working perfectly. I did not realize about the script's location! I have just put ´whatever.exe´ as arg for ´subprocess.Popen´ and specified the path with cwd argument. Thank you once again!

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