Dictionaries - returning a key sorted Dictionary

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#1

I would like to turn a dictionary into an “ordered” dictionary - i have an example here:

Dict1 = {
‘tim’ : ‘apple’,
‘bob’ : ‘banana’,
‘kim’ : ‘banana’,
‘bo’ : ‘apple’,
‘joe’ : ‘apple’
}

should return something like:

‘apple’ : [‘tim’, ‘bo’, ‘joe’],
‘banana’ : [‘bob’, ‘kim’]

How would I get around this? is there a built-in function or should i create this myself?

thanks!

#2

Hi Sören,

Python comes with a type called OrderedDict, but it’s very different from what you’re imagining. It’s also a pretty niche type since Python 3.7 - before then the order of keys in a dict was undefined.

It’s relatively easy to sort a dict by its keys:

>>> d
{'tim': 'apple', 'bob': 'banana', 'kim': 'banana', 'bo': 'apple', 'joe': 'apple'}
>>> dict(sorted(d.items()))
{'bo': 'apple', 'bob': 'banana', 'joe': 'apple', 'kim': 'banana', 'tim': 'apple'}
>>>

While this is what the title of your post suggests you want, it’s not what you’re actually asking, so let’s get on to that :slight_smile:

Luckily, this sort of manipulation is generally easy to do in Python. For your problem, I’d use defaultdict:

>>> from collections import defaultdict
>>> result = defaultdict(list)
>>> d
{'tim': 'apple', 'bob': 'banana', 'kim': 'banana', 'bo': 'apple', 'joe': 'apple'}
>>> for (key, value) in d.items():
...     result[value].append(key)
...
>>> result
defaultdict(<class 'list'>, {'apple': ['tim', 'bo', 'joe'], 'banana': ['bob', 'kim']})
>>>
#3 
Dict1 = {
    'tim' : 'apple',
    'bob' : 'banana',
    'kim' : 'banana',
    'bo' : 'apple',
    'joe' : 'apple'
}

transposed = {}
for k,v in Dict1.items():
    transposed.setdefault(v, []).append(k)

print(transposed)

{'apple': ['tim', 'bo', 'joe'], 'banana': ['bob', 'kim']}
1 Like
#4

Thanks a lot both! this was exactly the methods i was looking for!