Immutability and Python
andrea crotti
andrea.crotti.0 at gmail.com
Mon Oct 29 11:20:02 EDT 2012
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?
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