Refactoring Dilemma

George Sakkis george.sakkis at gmail.com
Mon Sep 11 03:27:59 CEST 2006


Carl Banks wrote:
> Kamilche wrote:
> > '''
> > I'm in the middle of a refactoring dilemma.
> > I have several singletons that I'm turning into modules, for ease of
> > access.
> > The usual method is noted as 'Module 1' below.
> > The new method is noted as 'Module 2'.
> > Is there any reason NOT to do this that I may be unaware of?
> > It's easier than remembering to declare global variables at the top of
> > the function.
> > '''
> >
> > # ----------- Module 1.py ------------
> > # Normal module processing
> > var = 0
> >
> > def MyRoutine():
> >     global var
> >     var = 1
> >
> > MyRoutine()
> > print var
> >
> >
> > # ----------- Module 2.py ------------
> > # 'Self' module processing
> > import sys
> > var = 0
> > self = sys.modules[__name__]
> >
> > def MyRoutine():
> >     self.var = 1
> >
> > MyRoutine()
> > print var
>
> I don't see any major problem with it.  In fact, I think it's a very
> good idea to do this, rather than use global statements, when using
> module as a singleton class.
>
> I recently made the same transition myself, though I solved it a bit
> differently.  I used a decorator to pass the module as the first
> argument (actually it passes a proxy to module's global dict, since the
> module itself isn't accesible from the function object).
>
> def modmethod(func):
>     class modproxy(object):
>         __getattribute__ = func.func_globals.__getitem__
>         __setattr__ = func.func_globals.__setitem__
>     self = modproxy()
>     def call_with_module(*args,**kwargs):
>         return func(self,*args,**kwargs)
>     call_with_module.func_name = func.func_name
>     return call_with_module
>
> @modmethod
> def MyRoutine(self):
>     self.var = 1
>
> MyRoutine()
> print var

This looks quite hackish, both the implementation and the usage; most
people would get confused when they didn't find var's assignment at
global scope. I prefer the the simple global statements if they aren't
that many, otherwise the assignment of the module to self is also fine.

George




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