Question

I have been searching the web for an answer now for quite a while, but this is giving me really headache:

I am using Ubuntu 12.04 and I want to execute a Python script from the terminal without using the full path.
So i added /home/kyril/python/scripts/ to the PATH variable through putting the following into ./bashrc:

kyrilpathvariable="/usr/lib/lightdm/lightdm:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/home/kyril/Python/scripts/:/home/kyril/Bash/scripts"

if [ "$kyrilpathvariable" = "$PATH" ]; then
    echo PATH already exported

else

PATH=$PATH:/home/kyril/Python/scripts/
PATH=$PATH:/home/kyril/Bash/scripts/
export PATH

fi

(I know the if clause is not necessary but I did not like to have everything two times in my PATH if I type exec bash.)

Now the problem: this perfectly works for my Bash scripts, so after making them executable via chmod I can just type $ script.sh and it is executed. However if I type $ python3 script.py the following error is raised: python3: can't open file 'script.py': [Errno 2] No such file or directory

if I type in the full path to the script it works. Anybody has an idea what I am doing wrong? Do I have to add the directory to the PYTHONPATH? (As I understood this only helps for importing modules).

Thanks guys!

Answer 1

When invoking python3 directly, python runs the script file you told it to, without using $PATH to find it. PYTHONPATH is irrelevant–that’s used for searching for Python modules.

I’m guessing you’re having issues with the wrong interpreter getting invoked when you run script.py by itself. I don’t know what the first line of your script is, but it should be this:

#!/usr/bin/env python3

Or if you need even finer control:

#!/usr/bin/env python3.2

And for Python 2 scripts:

#!/usr/bin/env python2

Or:

#!/usr/bin/env python2.7

You should check that these executables exist on your system before trying to use them.