In Python 2.7 with iPython:
>>> import os
>>> os.getenv??
Signature: os.getenv(key, default=None)
Source:
def getenv(key, default=None):
"""Get an environment variable, return None if it doesn't exist.
The optional second argument can specify an alternate default."""
return environ.get(key, default)
File: ~/venv/lib/python2.7/os.py
Type: function
So we can conclude os.getenv is just a simple wrapper around os.environ.get.