How to sort a dict of dicts by the length of a list inside child dicts

I’m a beginner to Python, and for the sake of learning I looked up some challenges to solve. Here I have a dictionary, containing several dictionaries, each having a list of dicts. My job here is to sort the dictionary, in descending order, based on which child of somedict has more elements in the key list.

somedict = {
    'a': {
        'key' : [{}, {}, ]
    },
    'b': {
        'key' : [{}, ]
    },
    'c': {
        'key' : [{}, {}, {} ]
    },
    'd': {
        'key' : [{}, {}, {}, ]
    },
    'e': {
        'key' : [{}, {}, {} ]
    },
    'f': {
        'key' : [{}, ]
    },
    'g': {
        'key' : [{}, {} ]
    },
    'h': {
        'key' : [{}, {}, {},]
    }

}

sorted_dict = sorted(somedict, key= lambda k: len(k['a']['key']))

print(sorted_dict)

While trying to use sorted(), I get:

TypeError: string indices must be integers

>Solution :

What you need to do is to sort the keys as a list, and from that sorted list rebuild the dict:

somedict = {
    ...
    # contents elided
}
keys = list(somedict.keys())
sorted_keys = sorted(keys, key= lambda k: len(somedict[k]['key']), reverse=True)

print(sorted_keys)

sorted_dict = {k:somedict[k] for k in sorted_keys}

print(sorted_dict)

Output

['c', 'd', 'e', 'h', 'a', 'g', 'b', 'f']
{'c': {'key': [{}, {}, {}]}, 'd': {'key': [{}, {}, {}]}, 'e': {'key': [{}, {}, {}]}, 'h': {'key': [{}, {}, {}]}, 'a': {'key': [{}, {}]}, 'g': {'key': [{}, {}]}, 'b': {'key': [{}]}, 'f': {'key': [{}]}}

And this can be shortened to one line:

sorted_dict = {k:somedict[k] for k in sorted(somedict, key=lambda k: len(somedict[k]['key']), reverse=True)}