Immutability and Python

[Jean-Michel Pichavant]

----- Original Message -----
> I have a philosofical doubt about immutability, that arised while
> doing
> the SCALA functional programming course.
> 
> Now suppose I have a simple NumWrapper class, that very stupidly
> does:
> 
> class NumWrapper(object):
>     def __init__(self, number):
>         self.number = number
> 
> and we want to change its state incrementing the number, normally I
> would do this
> 
>     def increment(self):
>         self.number += 1
> 
> 
> But the immutability purists would instead suggest to do this:
> 
>     def increment(self):
>         return NumWrapper(self.number + 1)
> 
> 
> Now on one hand I would love to use only immutable data in my code,
> but
> on the other hand I wonder if it makes so much sense in Python.
> 
> My impression is that things get more clumsy in the immutable form,
> for
> example in the mutable form I would do simply this:
> 
> number = NumWrapper(1)
> number.increment()
> 
> while with immutability I have to do this instead:
> new_number = number.increment()
> 
> But more importantly normally classes are way more complicated than
> my
> stupid example, so recreating a new object with the modified state
> might
> be quite complex.
> 
> Any comments about this? What do you prefer and why?
> --
> http://mail.python.org/mailman/listinfo/python-list
> 

"return NumWrapper(self.number + 1) "

still returns a(nother) mutable object.

So what's the point of all this ?

JM


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