python way to make integer class with additional data

Question

Good day! I'm think about class in python to store a map tiles inside, such as

map = [[WorldTile() for _ in range(10)] for _ in range(10)]

i create class

class WorldTile:
    def __init__(self, val):
        self.resource = val
        self.objects = dict()

    def __repr__(self):
        return self.resource

    def __str__(self):
        return '%s' % (str(self.resource))

    def __cmp__(self, other):
        return cmp(self.resource, other)

    def __add__(self, other):
        self.resource += other
        return self.resource

    def __sub__(self, other):
        self.resource -= other
        return self.resource

but something going wrong. i'l try

x = WorldTile.WorldTile(7)
print type(x), id(x), x
print x > 2, x < 5, x > 0
#x += 5
print type(x), id(x), x
print x, str(x), type(x)
print x.objects

they work fine, but if i'l uncomment line x += 5 x becoming an <type 'int'>

totally, i'm want to have class, with i can work as integer ( x = x +-*\ y etc ), but also can access additional fields if necessary ( x.objects ) i think i need override assignemet method, but that not possible in python. Any other way for me?

NPE · Accepted Answer · 2014-01-14 14:06:31Z

2

You could override __iadd__ for +=.

However, your current __add__ is broken. You could fix it by making it return a (new) instance of WorldTile rather than an int:

def __add__(self, other):
    return WorldTile(self.resource + other)

This will work for both + and += (handling self.objects is left as an exercise for the reader).

edited Jan 14, 2014 at 14:06

answered Jan 14, 2014 at 13:57

NPE

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2 Comments

thefourtheye Over a year ago

Interesting, I was making it to look like an int, with +, and you are making it to look like WorldTile.

wim Over a year ago

This is the correct way for classes which should model their behaviour after immutable builtins.

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