How to evaluate environment variables into a string in Python?

Question

I have a string representing a path. Because this application is used on Windows, OSX and Linux, we've defined environment variables to properly map volumes from the different file systems. The result is:

"$C/test/testing" 

What I want to do is evaluate the environment variables in the string so that they're replaced by their respective volume names. Is there a specific command I'm missing, or do I have to take os.environ.keys() and manually replace the strings?

Answer 1

Use os.path.expandvars to expand the environment variables in the string, for example:

>>> os.path.expandvars('$C/test/testing') '/stackoverflow/test/testing' 

Answer 2

In Python 3 you can do:

'{VAR}'.format(**os.environ)) 

for example

>>> 'hello from {PWD}'.format(**os.environ)) hello from /Users/william