A while back, a friend of mine who was working on a coding challenge for some internship. The prompt said to create a dictionary with string keys and string values in your favorite programming language, without using the built in dictionary type.
This got me thinking of how I would solve this, and this terrible monster is what I came up with:
class Dict: __getitem__ = getattr __setitem__ = setattr
This is a very silly solution. I don't feel bad about it. Here it is in action:
>>>d = Dict() >>>d['hi'] = 'test' >>>d['hi'] 'test'
How does it work? Well, in Python
__getitem__ is the protocol for
subscribtion access. When I write
d['hi'] Python internally calls
d.__getitem__('hi'). So whats the deal with the
getattr call then?
In Python, everything is an object. By default, objects internally map attribute names to values. In my dictionary implementation, I take advantage of this to use Python's internals to create my dictionary.
The pros of this dictionary are that it is fast. It is close (within 10%) of the builtin dictionary type (there is a bit of overhead with function calls).
There are quite a few cons, the first of which several of the more
knowledable among you have already realized. I'm totally cheating here.
Well, maybe. Or I'm not. Technically, classes use something called
types.MappingProxyType to manage attribute mappings. This is however an
implementation detail, so its up to personal opinion whether I'm using a built
in dictionary or not. Anyway, I think its pretty cool. And remember I did say
it was stupid...