How to make python class support item assignment?
built-in-types, inheritance, object-composition, python
Solution
Disclaimer : I might be wrong.
the notation :
self[something]
is legit in the Graph class because it inherits fro dict. This notation is from the dictionnaries ssyntax not from the class attribute declaration syntax.
Although all namespaces associated with a class are dictionnaries, in your class ChildObject, self isn't a dictionnary. Therefore you can't use that syntax.
Otoh, in your class Graph, self IS a dictionnary, since it is a graph, and all graphs are dictionnaries because they inherit from dict.
Problem
While looking over some code in Think Complexity, I noticed their `Graph` class assigning values to itself. I've copied a few important lines from that class and written an example class, `ObjectChild`, that fails at this behavior. ``` class Graph(dict): def __init__(self, vs=[], es=[]): for v in vs: self.add_vertex(v) for e in es: self.add_edge(e) def add_edge(self, e): v, w = e self[v][w] = e self[w][v] = e def add_vertex(self, v): self[v] = {} class ObjectChild(object): def __init__(self, name): self['name'] = name ``` I'm sure the different built in types all have their own way of using this, but I'm not sure whether this is something I should try to build into my classes. Is it possible, and how? Is this something I shouldn't bother with, relying instead on simple composition, e.g. `self.l = [1, 2, 3]`? Should it be avoided outside built in types? I ask because I was told "You should almost never inherit from the builtin python collections"; advice I'm hesitant to restrict myself to. To clarify, I know that `ObjectChild` won't "work", and I could easily make it "work", but I'm curious about the inner workings of these built in types that makes their interface different from a child of `object`.