How to iterate through a nested dict?

Question

I have a nested python dictionary data structure. I want to read its keys and values without using collection module. The data structure is like bellow.

d = {'dict1': {'foo': 1, 'bar': 2}, 'dict2': {'baz': 3, 'quux': 4}}

I was trying to read the keys in the dictionary using the bellow way but getting error.

Code

for key, value in d:
    print(Key)

Error

ValueError: too many values to unpack (expected 2)

So can anyone please explain the reason behind the error and how to iterate through the dictionary.

Asked By: Arijit Panda

||

Source

Answer 1

To get keys and values you need dict.items():

for key, value in d.items():
    print(key)

If you want just the keys:

for key in d:
    print(key)

Answered By: Stephen Rauch

Answer 2

Iterating through a dictionary only gives you the keys.

You told python to expect a bunch of tuples, and it tried to unpack something that wasn’t a tuple (your code is set up to expect each iterated item to be of the form (key,value), which was not the case (you were simply getting key on each iteration).

You also tried to print Key, which is not the same as key, which would have led to a NameError.

for key in d:
    print(key)

should work.

Answered By: Ken Wei

Answer 3

keys() method returns a view object that displays a list of all the keys in the dictionary

Iterate nested dictionary:

d = {'dict1': {'foo': 1, 'bar': 2}, 'dict2': {'baz': 3, 'quux': 4}}

for i in d.keys():
    print i
    for j in d[i].keys():
        print j

OR

for i in d:
    print i
    for j in d[i]:
        print j

output:

dict1 
foo
bar

dict2
baz 
quux

where i iterate main dictionary key and j iterate the nested dictionary key.

Answered By: bharatk

Answer 4

As the requested output, the code goes like this

    d = {'dict1': {'foo': 1, 'bar': 2}, 'dict2': {'baz': 3, 'quux': 4}}

    for k1,v1 in d.iteritems(): # the basic way
        temp = ""   
        temp+=k1
        for k2,v2 in v1.iteritems():
           temp = temp+" "+str(k2)+" "+str(v2)
        print temp

In place of iteritems() you can use items() as well, but iteritems() is much more efficient and returns an iterator.

Hope this helps 🙂

Answered By: Sunil Lulla

Answer 5

You could use benedict (a dict subclass) and the traverse utility method:

Installation: pip install python-benedict

from benedict import benedict

d = benedict({'dict1': {'foo': 1, 'bar': 2}, 'dict2': {'baz': 3, 'quux': 4}})

def traverse_item(dct, key, value):
   print('key: {} - value: {}'.format(key, value))

d.traverse(traverse_item)

Documentation: https://github.com/fabiocaccamo/python-benedict

Note: I am the author of this project.

Answered By: Fabio Caccamo

Answer 6

if given dictionary pattern has monotone format and keys are known

dict_ = {'0': {'foo': 1, 'bar': 2}, '1': {'foo': 3, 'bar': 4}}
for key, val in dict_.items():
    if isinstance(val, dict):
        print(val.get('foo'))
        print(val.get('bar'))

in this case we can skip nested loop

Answered By: shivaraj karki

Answer 7

you can iterate all keys and values of nested dictionary as following:

d = {'dict1': {'foo': 1, 'bar': 2}, 'dict2': {'baz': 3, 'quux': 4}}

for i in d:
    for j, k in d[i].items():
        print(j,"->", k)

Your output looks like this –

foo -> 1
bar -> 2
baz -> 3
quux -> 4

Answered By: mksmahi

Answer 8

The following will work with multiple levels of nested-dictionary:

def get_all_keys(d):
    for key, value in d.items():
        yield key
        if isinstance(value, dict):
            yield from get_all_keys(value)


d = {'dict1': {'foo': 1, 'bar': 2}, 'dict2': {'dict3': {'baz': 3, 'quux': 4}}}
for x in get_all_keys(d):
    print(x)

This will give you:

dict1
foo
bar
dict2
dict3
baz
quux

Answered By: 0x0

How to iterate through a nested dict?

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