How to extend OrderedDict with defaultdict behavior

Question

I have a list of OrderedDict objects. I would like to combine all of them together and then sort them by the fruit attribute in each of them. I have been trying to combine and sort them using defaultdict using the code below:

super_dict_apple = defaultdict(list)
super_dict_orange = defaultdict(list)
super_dict_no_fruit = defaultdict(list)


for d in dict:
        if 'fruit' not in d:
            for k, v in d.iteritems():
                super_dict_no_fruit[k].append(v)
        elif d['fruit'] == 'Apple':
            for k, v in d.iteritems():
                super_dict_apple[k].append(v)
        elif d['fruit'] == 'orange':
            for k, v in d.iteritems():
                super_dict_orange[k].append(v)

With this I get one key and all the associated values, but I lose the original order. So I tried to do it with an OrderedDict, but I cannot get it to work. This is what I tried:

from collections import OrderedDict

order_dict_no_fruit = OrderedDict()
order_dict_apple = OrderedDict()
order_dict_orange = OrderedDict()

for d in dict:
        if 'fruit' not in d:
            for k, v in d.iteritems():
                order_dict_no_fruit[k].append(v)
        elif d['fruit'] == 'Apple':
            for k, v in d.iteritems():
                order_dict_apple[k].append(v)
        elif d['fruit'] == 'orange':
            for k, v in d.iteritems():
                order_dict_orange[k].append(v)

My main goal is to keep the original order of the dictionaries but combine them into three different OrderedDict objects based on the fruit keys.

**How does it not work**. You should always be able to describe that in detail. — juanpa.arrivillaga, Feb 23 '17 at 00:13
Please show an example of what you're getting and another example of what you expect. — Soviut, Feb 23 '17 at 00:15
Likely, it doesn't work because an `OrderedDict` is not a `defaultdict` so it doesn't automatically set a default value when accessing. If only there were `dict` method that *setdefault*...DOTDOT — juanpa.arrivillaga, Feb 23 '17 at 00:15

score 9 · Accepted Answer · answered Feb 23 '17 at 00:30

9

Instead of a regular OrderedDict, try a subclass that adds in defaultdict behavior:

class OrderedDictWithDefaultList(OrderedDict):
    def __missing__(self, key):
        value = list()
        self[key] = value
        return value

answered Feb 23 '17 at 00:30

Raymond Hettinger

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'TypeError: 'type' object has no attribute '__getitem__'' – user3609179 Feb 23 '17 at 00:35
You've got an error elsewhere in your code. Perhaps you left off the parentheses off when instantiating the dictionaries. It should be ``super_dict_apple = OrderedDictWithDefaultList()`` instead of ``super_dict_apple = OrderedDictWithDefaultList``. – Raymond Hettinger Feb 23 '17 at 00:58

How to extend OrderedDict with defaultdict behavior

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