Forgot my wrapup of example! Sorry!

[Steve Holden]

GMane Python wrote:
> So, I forgot the last part of my example that might gel in your mind why
> Objects are useful in certain situations.  Ok so you maybe followed my
> example of the shopping cart.  Let's just forget for a moment the use for
> shopping carts is for  websites.  Let's just say you were going to write the
> lines directly into Python, like maybe at the IDLE interpreter.  Like maybe
> you're testing the functionality of the routine for correctness, not actual
> implementation.
> 
> 
[good introductory class stuff snipped]
> 
> 
> In a class, you can have a variable 'total' and you can have a variable
> 'self.total'.  The first is just accessible from within the structure of the
> class.  The latter is accessible from outside the class.  So, using a class
> with the variable self.total, you can from outside the class say:
> 
> 
> 
> print ShoppingCart["Dave"].total
> 
> 
> 
> to get the value of the variable self.total.  (That had me buggered for a
> while ..... )
> 
Thanks for the smile this gave me. We all get to this stage periodically 
when programming.
> 
> 
> If you can wrap your mind around this, you're well on your way to using OOP
> I believe.  If not, , don't give up. I'm just a python/programming newbie
> and maybe missed the boat completely with my posting.
> 
Well maybe you did, but you actually managed to demonstrate important 
parallels between namespaces and dictionaries in Python.
> 
> 
> Another quite important part I didn't even mention was sub-classing.  That's
> taking a class, and 'inheriting' it's code to your class as a base, then you
> can re-write or adddifferent methods.  But, first I think it's important to
> understand how to have several instances of a single class running in
> memory, each with different values for the defined variables.  I'll let
> someone else talk about that.
> 
As indeed they almost inevitably will :-)

regards
  Steve
-- 
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