code: def envget(var, default=None):
      
  
      if 'pyraf' in sys.modules:
          #ONLY if pyraf is already loaded, import iraf into the namespace
          from pyraf import iraf
      else:
          # else set iraf to None so it knows to not use iraf's environment
          iraf = None
  
      try:
          if iraf:
              return iraf.envget(var)
          else:
              raise KeyError
      except KeyError:
          try:
              return _varDict[var]
          except KeyError:
              try:
                  return os.environ[var]
              except KeyError:
                  if default is not None:
                      return default
                  elif var == 'TERM':
                      # Return a default value for TERM
                      # TERM gets caught as it is found in the default
                      # login.cl file setup by IRAF.
                      print("Using default TERM value for session.")
                      return 'xterm'
                  else:
                      raise KeyError("Undefined environment variable `%s'" % var)
docs: Get value of IRAF or OS environment variable.