Python: Not all environment variables present in os.environ

Question

In the python shell, using

import os 
print os.environ 

prints the complete list of environment variables with nothing missing. However when I call the interpreter with a filename:

sudo python file.py 

and use

import os 
print os.environ 

I see that some of the environment variables are missing in the dict.

Why do they behave differently?

Operating system: Ubuntu 14.04

Answer 1

I saw this happen when ENV Vars were not set using export in bash, so they were not propagating to the python script.

Answer 2

I realised that the difference was because I was using sudo during the execution for the second where the environment was not preserved. I need to add those environment variables to my sudoers file or preserve them during execution.