Is there any trick to "overload the dot operator"?

Question

I know the question is a little weirdly stated, but I can't think of any other way of saying it. I have an application that deals with large json objects, and I want to be able to just say:

object1.value.size.whatever.attributexyz 

instead of

object1.get('value').get('size').get('whatever').get('attributexyz') 

Is there some clever way to catch the AttributeError that would be raised and check inside the data structure if that attribute corresponds to any of its values?

Answer 1

In object1's class definition,

def __getattr__(self, key):     return self.get(key) 

Any attempt to resolve a property, method, or field name that doesn't actually exist on the object itself will be passed to __getattr__.

If you don't have access to the class definition, i.e. it's something like a dictionary, wrap it in a class. For a dictionary, you could do something like:

class DictWrapper(object):     def __init__(self, d):         self.d = d     def __getattr__(self, key):         return self.d[key] 

Note that a KeyError will be raised if the key is invalid; the convention, however, is to raise an AttributeError (thanks, S. Lott!). You can re-raise the KeyError as an AttributeError like so, if necessary:

try:     return self.get(key) except KeyError as e:     raise AttributeError(e) 

Also remember that if the objects you are returning from __getattr__ are also, for example, dictionaries, you'll need to wrap them too.