I thought I throw together a little dirty script on our server (Ubuntu 16.04) that gives me some plain text output from Python.
I want to call the script like this f
Run PIP with root user.
That should fix the problem.
I recommend that you try the solution that xotihcan posted first as that is the easy way to make most python modules available to all users including www-data. However it doesn't work for every python module. If that doesn't work for you or you just want to install modules for the www-data user only then use the following commands:
sudo mkdir /var/www/.local
sudo mkdir /var/www/.cache
sudo chown www-data.www-data /var/www/.local
sudo chown www-data.www-data /var/www/.cache
sudo -H -u www-data pip install CoolProp
I had this same issue trying to make the Python pyro4 module available for the www-data use. There is another way to do it but it involves some even dirtier hackery. For more details check out my question/answer @ How do I properly call a Python Pyro client using PHP and Apache web server?