Access instance variable name within class

Question

A little background - I am playing around with pygame, and want to create a dictionary of all Mob class instances' positions.

The way I see it:

human = Mob(pos)
mob_positions = {human : pos}

So every time I call Mob.__init__() I wanted to add a pos to mob_positions dict.

How do I access current instance variable name? Or is it extremely wrong approach?

orlp · Accepted Answer · 2012-08-11 13:32:06Z

2

Any bound method, including __init__, takes at least one parameter, usually named self, which is exactly what you are describing.

class Mob(object):
    def __init__(self, pos):
        mob_positions[self] = pos

answered Aug 11, 2012 at 13:32

orlp

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2 Comments

Ignacio Vazquez-Abrams Over a year ago

Well, it takes however many parameters you define it to take. But it does take at least one.

orlp Over a year ago

@IgnacioVazquez-Abrams: I changed my wording.

Rostyslav Dzinko · Accepted Answer · 2012-08-11 13:33:45Z

2

You have several ways to solve the problem. One of them is to pass mob_positions dictionary as argument to __init__.

class Mob(object):
    def __init__(self, pos, field=None):
        ...
        if field:
            field[self] = pos

Such notation allows you to place mobs on initialization or not (depending on what you're doing with mobs).

answered Aug 11, 2012 at 13:33

Rostyslav Dzinko

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2 Comments

Ruslan Osipov Over a year ago

Right, I guess I was confused by result of the print, dictionary dump after using self was {<Mob sprite(in 0 groups)>: pos}. Thanks

Rostyslav Dzinko Over a year ago

<Mob sprite(in 0 groups)> is just a representation of your object. You just need to override __repr__() method of your mob class to receive some meningful representation (e.g. mob's name or mob's number, or smth. else you want to distinct mobs with).

Antimony · Accepted Answer · 2012-08-11 13:32:22Z

1

The current instance variable is simply the first argument to the function. By convention it is named self.

Here's how I'd do things.

class Mob(object):
    def __init__(self, pos, mob_positions):
        self.pos = pos
        mob_positions[self] = pos

answered Aug 11, 2012 at 13:32

Antimony

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