global variables or inheritence

Donn Cave donn at u.washington.edu
Thu Apr 27 00:03:52 CEST 2000


Quoth Thomas Rasmussen <simpsons at kom.auc.dk>:
...
| Well i'm programming a small admin tool, which must use the users
| $EDITOR for editing files. This works fine if the EDITOR sysenv is
| set, if not, then i want to ask the user which editor he want to use,
| and then pass this variable to the module that handles
| filemanipulation. This modules is also in another file if it
| matters... I must add that this is my first real program made in
| python...

When things get difficult in Python, my reflex is to write a
big hairy class.  Maybe something like this would work, or at
least give you an idea:

  import os
  import sys

  class UserEditor:
          def __init__(self, default_editor = None):
                  self.program = default_editor
          def get(self):
                  if not self.program:
                           try:
                                    self.program = os.environ['EDITOR']
                           except KeyError:
                                    sys.stdout.write('Editor? ')
                                    ... etc.
                  return self.program
          def set(self, editor):
                  self.program = editor
          def invoke(self, file):
                  program = self.get()
                  return os.system('%s %s' % (program, file)) == 0

  editor = UserEditor()


Let's say that's at module scope in the "interfaces" module.  In other
modules you may say

  filemanipulation.xyzfile(interfaces.editor.get(), ...)

or maybe this class will turn out to be a convenient place to do some
stuff that is now cluttering up filemanipulation, so you should say

  filemanipulation.xyzfile(interfaces.editor, ...)

	Donn Cave, University Computing Services, University of Washington
	donn at u.washington.edu



More information about the Python-list mailing list