python object style access for dictionaries ; cant figure it out

Question

class ObjectDict(dict):
    """ allows object style access for dictionaries """

    def __getattr__(self, name):
        if name in self:
            return self[name]
        else:
            raise AttributeError('No such attribute: %s' % name)

    def __setattr__(self, name, value):
        self[name] = value

    def __delattr__(self, name):
        if name in self:
            del self[name]
        else:
            raise AttributeError('No such attribute: %s' % name)

can someone explain this code for me ? I'm just a python beginner.

What specifically do you need help understanding? This is far too broad. — Carcigenicate, Mar 01 '18 at 13:23
Related - https://stackoverflow.com/questions/4295678/understanding-the-difference-between-getattr-and-getattribute — OneCricketeer, Mar 01 '18 at 13:31

OneCricketeer · Answer 1 · 2018-04-01T18:52:09.377

An ObjectDict instance is a regular dictionary via class inheritance. See ObjectDict(dict)

The __getattr__ magic function allows for the definition of dot-notation access for any object. And it simply calls normal dictionary access here

Similarly, __setattr__ and __delattr__ allows setting and deleting (using Python's del expression) values from dot-notation. However, to set nested values, you need the value of the first key to also be an ObjectDict

score 1 · Accepted Answer · edited Apr 01 '18 at 18:51

__getattr__ is for when you want to get a data.

__setattr__ is for when you want to set a data.

__delattr__ is for when you want to del a data.

Now, the methods should be quite clear.

def __getattr__(self, name):
    # if the key exists... return it.
    if name in self:
        return self[name]
    # if not : raise an error.
    else:
        raise AttributeError('No such attribute: %s' % name)

def __setattr__(self, name, value):
    # set VALUE as value, with NAME as key in the dict.
    self[name] = value

def __delattr__(self, name):
    # if the key "name" exists in the dictionnary... delete it
    if name in self:
        del self[name]
    # else, it doesnt exist, so cant delete it.
    else:
        raise AttributeError('No such attribute: %s' % name)

I invite you to accept the answer if you found it the most helpful to you. :) — IMCoins, Mar 03 '18 at 13:41

python object style access for dictionaries ; cant figure it out

2 Answers2