From: avdi@... (Avdi B. Grimm)
Date: 2002-09-10T10:10:44+09:00
Subject: Re: Larry Wall's comments on Ruby

>  Python was always OO insofar as its implementation of OO can be
>  called OO.

Would that this were so.  However, it's not; and no amount of claiming
that it was will change history.  In the words of the Python FAQ:

   6.7. Why must 'self' be declared and used explicitly in method
   definitions and calls?

   ...When classes were added to Python, this was (again) the simplest
   way of implementing methods without too many changes to the
   interpreter.

   [The FAQ then proceeds to spend a couple paragraphs attempting to
   rationalize why this is a feature, not a bug]


Python's OO is bolted on, and it shows.  It's true that it was bolted
on at a much younger stage than Perl's, long before it came to massive
popularity.  But as the Python FAQ admits, the reason you have to hold
the compiler's hand in Python by explicitly declaring the 'self'
variable is was *not* a conscious design choice, as some have later
come to claim.  It is that way because that was the easiest way to
kludge OO support in, and no one ever got around to fixing it.  This
also the reason that Pythons types and classes were not unified until
very recently, and why old Python code uses the procedural
'String.foo(mystring)' functions rather than the more OO
'mystring.foo()' methods.

The strongest argument for this design is that since Python doesn't
have variable declarations (like Ruby), you need a way to tell the
compiler you are creating an instance variable rather than a local
variable.  A closely related argument is that it's an aid to the
reader to have instance variables clearly marked wherever they are
used.  Ruby neatly solves this with the '@foo' notation.  Python,
eschewing "funny characters", could still have solved this by making
'self' a keyword and requiring all uses of instance variables use the
'self.foo' notation. 

Don't tell any of this to a loyal Python user though, if you value
your hide.  One of the reasons I prefer both Perl and Ruby over Python
for most tasks is just this - the community.  Perl users - and Larry
himself - are perfectly happy to admit that Perl's OO is a bolted-on
hack (albeit a clever one).  And Ruby was OO from inception.  On the
other hand the Python crowd would, in my experience, prefer to explain
to you at length why it's your definition of OO that's flawed, rather
than the language.

~Avdi