Immutability and Python

[Ian Kelly]

On Mon, Oct 29, 2012 at 10:12 AM, andrea crotti
<andrea.crotti.0 at gmail.com> wrote:
> Also because how doi I make an immutable object in pure Python?

I sometimes use namedtuples for this.

from collections import namedtuple

MyImmutableClass = namedtuple('MyImmutableClass', 'field1 field2 field3 field4')

If you want default arguments then use a factory function.  Or if you
want the class to have methods, then subclass it:

_MyImmutableClass = namedtuple('MyImmutableClass', 'field1 field2
field3 field4')

class MyImmutableClass(_MyImmutableClass):

    def __new__(cls, field1, field2, field3=None, field4=42):
        return super().__new__(cls, field1, field2, field3, field4)

    def get_sum(self):
        return self.field1 + self.field2

Cheers,
Ian