Immutability and Python

[Paul Rubin]

andrea crotti <andrea.crotti.0 at gmail.com> writes:
> and we want to change its state incrementing the number ...
>  the immutability purists would instead suggest to do this:
>     def increment(self):
>         return NumWrapper(self.number + 1)

Immutability purists would say that numbers don't have "state" and if
you're trying to change a number's state by incrementing it, that's not
immutability.  You end up with a rather different programming style than
imperative programming, for example using tail recursion (maybe wrapped
in an itertools-like higher-order function) instead of indexed loops to
iterate over a structure.