Convert a list of dictionaries to a dictionary of dictionaries

Question

I need to convert a list of dictionaries to a dictionary of dictionaries, with a particular item as the new key.

This is the way I'm currently doing it:

>>> a
[{'bar': 'baz', 'id': 'foo'}, {'bar': 'baz', 'id': 'qux'}]
>>> {
    item['id']:{
        sub_item:item[sub_item] for sub_item in item if sub_item != 'id'
    } for item in a}

{'qux': {'bar': 'baz'}, 'foo': {'bar': 'baz'}}

However, this looks really ugly to me. Is there a more elegant way to do this?

Answer 1

While using methods with side effects in list- or dict-comprehensions is generally frowned upon, in this case you could make use of dict.pop to get the id and at the same time remove it from the dictionary.

>>> a = [{'bar': 'baz', 'id': 'foo'}, {'bar': 'baz', 'id': 'qux'}]
>>> {d.pop("id"): d for d in a}
{'qux': {'bar': 'baz'}, 'foo': {'bar': 'baz'}}

Keep in mind, though, that this will alter the dictionary in-place, i.e. afterwards:

>>> a
[{'bar': 'baz'}, {'bar': 'baz'}]

If you do not want to alter the original dictionaries, use map(dict, a) to create copies before poping elements from those, leaving the original dicts in a as they were.

>>> {d.pop("id"): d for d in map(dict, a)}
{'qux': {'bar': 'baz'}, 'foo': {'bar': 'baz'}}

Answer 2

I would recommend an object-oriented approach to this.

>>> class Buz(object):
...     def __init__(self, bar):
...             self.bar = bar
...
>>> buzdict = {'foo':Buz('baz'), 'qux':Buz('baz')}
>>> buzdict.get('foo').bar
'baz'
>>> buzdict.get('qux').bar
'baz'