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?

Answer 1

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

• Ignacio Vazquez-Abrams: Well, it takes however many parameters you define it to take. But it does take at least one.
• orlp: @IgnacioVazquez-Abrams: I changed my wording.

Answer 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).

• Ruslan Osipov: 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: <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).

Answer 3

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