CODEWITHSUNDEEP
pythonsortingdictionary
Laghorn
Laghorn

Reputation: 43

Print Keys of nested dictionaries in sorted order in Python

I am learning a bit of Python at the moment. One of the first tasks I face is to print the keys of a dictionary and its possible nested dictionaries in sorted order.

The task definition is:

Write a program to display all the keys of a 'dictionary of dictionaries' (nested dictionary) in sorted order

So I have something like

vDict={1:2942, 5:{20:231, 49:359, 65:429}, 39:{9359:2932, 9298:29328, 124:4}}

and need to print all of its keys in sorted order. Theoretically, I am not aware of modules so I can only use built in functions

In my mind, the only way I can come up with is to use the output of vDict.keys() function and split with regex in order to sort the values. But then I have no idea how to iterate through tier 2 dictionaries.

I am pretty sure that is not what I am supposed to do here and there is an easier way. I would be interested to see how an educated mind approaches this.

This is a self study during calm work hours so you are not doing my homework here ;)

Upvotes: 0

Views: 99

Answers (3)

shargors
shargors

Reputation: 2157

This should do it:

def process(dd, keys):

    for key, val in dd.items():
        keys.append(key)
        if isinstance(val,dict):
            process(val, keys)

    return keys


vDict={1:2942, 5:{20:231, 49:359, 65:429}, 39:{9359:2932, 9298:29328, 124:4}}

keys=[]
process(vDict, keys)
print(sorted(keys))

Upvotes: 3

Holloway
Holloway

Reputation: 7377

The oneliner approach

>>> sorted([k for v in vDict.values() if isinstance(v, dict) for k in v] + list(vDict))
[1, 5, 20, 39, 49, 65, 124, 9298, 9359]

The split out, slightly more readable version

>>> def iterate_keys(d):
...     for k, v in d.items():
...         yield k
...         if isinstance(v, dict):
...             yield from v
...
>>> sorted(iterate_keys(vDict))
[1, 5, 20, 39, 49, 65, 124, 9298, 9359]

If you wanted to handle dictionaries with deeper nesting, you could change the yield from v line to yield from iterate_keys(v) to visit all levels of nesting.

Upvotes: 3

Pragya
Pragya

Reputation: 111

I think this is what you are looking for: 

vDict={1:2942, 5:{20:231, 49:359, 65:429}, 39:{9359:2932, 9298:29328, 124:4}}
def get_keys(vDict):
    keys_list = []

    for k in vDict.keys():
        keys_list.append(k)
        if(type(vDict[k]) is dict):
            keys_list = keys_list + get_keys(vDict[k])
    return keys_list
new_list = get_keys(vDict)
new_list.sort()

Output: 

[1, 5, 20, 39, 49, 65, 124, 9298, 9359]

Upvotes: 2

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