How to implement __iter__(self) for a container object (Python)

Question

I have written a custom container object.

According to this page, I need to implement this method on my object:

__iter__(self)

Howe

Answer 1

In case you don't want to inherit from dict as others have suggested, here is direct answer to the question on how to implement __iter__ for a crude example of a custom dict:

class Attribute:
    def __init__(self, key, value):
        self.key = key
        self.value = value

class Node(collections.Mapping):
    def __init__(self):
        self.type  = ""
        self.attrs = [] # List of Attributes

    def __iter__(self):
        for attr in self.attrs:
            yield attr.key

That uses a generator, which is well described here.

Since we're inheriting from Mapping, you need to also implement __getitem__ and __len__:

    def __getitem__(self, key):
        for attr in self.attrs:
            if key == attr.key:
                return attr.value
        raise KeyError

    def __len__(self):
        return len(self.attrs)