Python: getting the home directory for a user

# home_dir is different for a web user and for a native user on a web server
# So, do the following check
if os.environ.has_key("DOCUMENT_ROOT"):
  doc_root = os.environ["DOCUMENT_ROOT"]
        home_dir = get what you need from doc_root
  #home_dir = doc_root.split("something")[0]
elif os.environ.has_key("HOME"):
  doc_root = os.environ["HOME"]
  home_dir = doc_root+"/"