CODEWITHSUNDEEP
pythonlistdictionary
mylearning
mylearning

Reputation: 65

How to get key from a specific value in a dictionary containing list

Suppose I have a dictionary

d={'name1': ['A1', 'A2', 'A3', 'A4'], 'name2': ['E1', 'F1', 'G1'], 'name3'=['E3','F3']}

How can I get the key of a specific value. For example, input='A1' then output='name1'. I was thinking to create a function like below, but it might not working (return None) because of the list in dictionary

def reverse_search(dictionary, value):
    keys = dictionary.keys()
    for key in keys:
        if dictionary.get(key) == value:
            return key

I really appreciate any help!

Upvotes: 0

Views: 678

Answers (5)

bulutgonulalan
bulutgonulalan

Reputation: 356

I think the easiest way like this

d = {'name1': ['A1', 'A2', 'A3', 'A4'],
     'name2': ['E1', 'F1', 'G1'],
     'name3': ['E3', 'F3']
     }


def filter_dict(search_key):
    k, v = tuple(filter(lambda x: search_key in x[1], d.items()))[0]
    return k


search_key = 'A1'
print(filter_dict(search_key))

Upvotes: 1

Amit Nanaware
Amit Nanaware

Reputation: 3356

try below code:

d = {'name1': ['A1', 'A2', 'A3', 'A4'],'name2': ['E1', 'F1', 'G1'], 'name3' : ['E3', 'F3']}
s = 'A1'
o = list(filter(lambda x:s in x[1],d.items()))[0][0]
print(o)

Upvotes: 1

Selcuk
Selcuk

Reputation: 59444

It is more performant to construct a reverse dictionary first if you are going to do this multiple times:

>>> reverse_lookup = {k: v for v, l in d.items() for k in l}

then

>>> reverse_lookup['A1']
'name1'
>>> reverse_lookup['G1']
'name2'

Upvotes: 1

Raunak Jalan
Raunak Jalan

Reputation: 83

You can check in list if that value exists:

def reverse_search_from_dictionary(dictionary, value):
    keys = dictionary.keys()
    for key in keys:
        if value in dictionary.get(key):
            return key
    return "Not present"

Upvotes: 1

azro
azro

Reputation: 54168

You're near to get it, but the dict's values are list so you can't use ==, because ['A1', 'A2', 'A3', 'A4'] != 'A1' you need to test for inclusion with in

def reverse_search_from_dictionary(dictionary, value):
    keys = dictionary.keys()
    for key in keys:
        if value in dictionary[key]:  # no need of 'get', you're sure the key is present
            return key

Nicer with iteration on both pairs and values

def reverse_search_from_dictionary(dictionary, keyword):
    for key, values in dictionary.items():
        if keyword in values:
            return key

Upvotes: 4

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