Retrieve keys using values from a dictionary

Question

Basically I am trying to find a way to get the key of a value from a dictionary by searching the value.

people = {
    "Sarah" : "36",
    "David" : "42",
    "Ricky" : "13"
    }


user_input = ('Enter the age of the individual") #The user enters the 
                                                 #value 
key_to_output = (...) #The variable that would contain the key value
print(key_to_output)

For example in the dictionary above if the user enters "36", they would be returned have "Sarah" returned. The dictionary I am using will never have a overlapping values so don't worry about any issues that would cause.

Also, because my python knowledge isn't very advanced it would be much appreciated if the responses were kept quite amateur so I can understand them properly.

This question is a duplicate of https://stackoverflow.com/questions/8023306/get-key-by-value-in-dictionary — David Buck, Nov 02 '19 at 17:15
What if the dict is `people = { "Sarah" : "36", "David" : "36", "Ricky" : "13" }` What answer do you want if you search for `36`? `["Sarah", "David"]`? Either one? ` — Martin Bonner supports Monica, Nov 02 '19 at 17:28
Does this answer your question? [Get key by value in dictionary](https://stackoverflow.com/questions/8023306/get-key-by-value-in-dictionary) — Martin Bonner supports Monica, Nov 02 '19 at 17:33

pka32 · Accepted Answer · 2019-11-02T17:37:47.813

2

You can invert the dictionary as so -

people_inv = {v:k for k,v in people.items()}

Now say your user inputted 36,

user_input = "36"
people_inv[user_input] # this will give Sarah

If the values are not unique like in the example below, you can do this -

people = {"Sarah":36, "Ricky":36, "Pankaj":28} 
people_inv= {}
for k,v in people.items():
    people_inv.setdefault(v, []).append(k)
people_inv["36"]

Output

['Sarah', 'Ricky']

edited Nov 02 '19 at 17:37

answered Nov 02 '19 at 17:14

pka32

5,176
1
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How would I go about turning the line people_inv['36'] into people_inv[x] where x = the user_input? I tried print(people[user_input]) but got a key error when i entered 36. – Richard302 Nov 02 '19 at 17:28
@Richard302 `x = int(user_input)` – Martin Bonner supports Monica Nov 02 '19 at 17:30

NameVergessen · Answer 2 · 2019-11-02T17:21:48.710

1

The easyest way would be to itterate over the values like this.

    def find_key(value, people):
        for name in people:
            if people[name] == value:
                return name

If you are trying to get mutliple keys I would try:

   def find_key(value, people):
       names = []
       for name in people:
           if people[name] == value:
               names.append(name)
       return names

edited Nov 02 '19 at 17:21

answered Nov 02 '19 at 17:16

NameVergessen

598
8
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Thank you for the response I shall also try this format out! – Richard302 Nov 02 '19 at 17:29

Retrieve keys using values from a dictionary

2 Answers2