Private methods

[Roy Smith]

In article 
<1krpdak.u0qy9e1a4knspN%real-not-anti-spam-address at apple-juice.co.uk>,
 real-not-anti-spam-address at apple-juice.co.uk (D.M. Procida) wrote:

> Mark Lawrence <breamoreboy at yahoo.co.uk> wrote:
> 
> > On 09/10/2012 14:24, D.M. Procida wrote:
> > > What exactly is the point of a private method? Why or when would I want
> > > to use one?
> > >
> > > Daniele
> > >
> > 
> > Hardly a Python question but using a search engine could have got you
> > here, and rather faster :) 
> >
> http://stackoverflow.com/questions/2620699/why-private-methods-in-the-ob
> ject-oriented
> 
> Thanks. Sometimes I prefer to talk to real people on Usenet than do web
> searches. Just my preference.
> 
> Anyway, one of the answers on that page explains that public methods are
> interfaces to a class, that other things might rely on, and private ones
> are for its own internal logic, that other things don't need to care
> about.
> 
> In Python, using an underscore is simply a convention to note that a
> method is private - it doesn't actually hide it from other things -
> correct?

Yes (modulo some details of how import works that I've never fully 
figured out and which lack of knowledge hasn't seemed to have hurt me 
any).

I view public and private in Python this way:

Public: I hereby declare that this method or attribute is part of the 
promised never to change interface of this class.  I might possibly 
break that promise at some point in the future, but if I do, you have 
the right to bitch and whine about it, and I'm morally obligated to at 
least pretend I care.

Private: I hereby declare that this method or attribute is something I 
needed to have for my own purposes, and is officially hidden inside my 
kimono.  Like all things inside my kimono, you may speculate about their 
existence all you want, but you touch them at your own peril.  I may 
change them at some point in the future, and while you can bitch and 
whine about it all you want, I'm not listening.