Re: Immutability and Python

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From	Ian Kelly <ian.g.kelly@gmail.com>
Date	2012-10-29 13:23 -0600
Subject	Re: Immutability and Python
Newsgroups	comp.lang.python
Message-ID	<mailman.3043.1351538616.27098.python-list@python.org> (permalink)

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On Mon, Oct 29, 2012 at 10:12 AM, andrea crotti
<andrea.crotti.0@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

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Re: Immutability and Python Ian Kelly <ian.g.kelly@gmail.com> - 2012-10-29 13:23 -0600

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