Getting only one value that matches my search in a dictionary

Question

So I want to go over a dictionary searching for the value True. If it finds it, I'd like to return the Key that matched with the value.

I tried using d.get(True) but that returns all of the keys. I only need the first one it could find.

Any ideas how to do so?

Thanks

If you need to search a key in a dict by its value then you are doing *something* wrong. It beats the entire purpose of using a dict — DeepSpace, Aug 27 '19 at 15:16

score 0 · Accepted Answer · answered Aug 27 '19 at 15:17

0

Just loop over the dictionary with for

d = {...}

for i in d:
    if d[i]:
        return i

That, or the dictionary should be "backwards" to what you are using. That would be the correct way of using a dictionary.

d = {True: [...], False: [...]}

answered Aug 27 '19 at 15:17

ofthegoats

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Don't rush posting an answer until you're positive that it's **complete** and correct. Hint: `return i` :) – CristiFati Aug 27 '19 at 15:18
I hadn't thought of DeepSpace's clever remark yet – ofthegoats Aug 27 '19 at 15:20
`if d[i]:` is true for any truthy value that `d[i]` holds. – Austin Aug 27 '19 at 15:22

score 0 · Answer 2 · answered Aug 27 '19 at 15:18

you could create a reverse lookup dictionary:

from collections import defaultdict

dct = {a: bool(a & 1) for a in range(7)}
# {0: False, 1: True, 2: False, 3: True, 4: False, 5: True, 6: False}

rev = defaultdict(list)
for key, value in dct.items():
    rev[value].append(key)
# defaultdict(<class 'list'>, {False: [0, 2, 4, 6], True: [1, 3, 5]})

now rev[True] would return all the previous keys that had True as value.

Getting only one value that matches my search in a dictionary

2 Answers2