What is a more efficient way to extract sub-dicts from a list of dicts in python?

Question

I have a json like this:

{
    "team": [
        {
            "id": "1",
            "member_name": "name1",
            "some_other_key":"keyvalue1"                
        },
        {
            "id": "2",
            "member_name": "name2",
            "some_other_key": "keuvalue2"

        }
    ]
}

And I want to create a dict like this

 { "1": "name1","2":"name2"}

I have written code like this

user_mapping = {}
for user in users['team']:
    user_mapping[user['id']] = user['member_name']

but I wanted to know if there's a more pythonic way or efficient way to do this than the brute force approach I've used.

How could you do this *other* than "brute force"? You have to iterate over all of the items. — jonrsharpe, Oct 16 '19 at 10:34
@GPhilo neither of those use a different *algorithm*, though, do they? They're still brute force insofar as they can't take shortcuts to get to the result; it's a fundamentally O(n) operation. — jonrsharpe, Oct 16 '19 at 10:41

score 4 · Answer 1 · answered Oct 16 '19 at 10:33

4

Simply and straightforward:

user_mapping = {user['id']: user['member_name'] for user in users['team']}

Besides, your for loop approach is not a "brute-force". You would use the former approach when you need a more extended logic (with intermediate statements/conditions/expressions).

answered Oct 16 '19 at 10:33

RomanPerekhrest

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Is dict comprehension faster in this case? – Sujay DSa Oct 16 '19 at 10:39
1

@SujayDSa https://stackoverflow.com/questions/52542742/why-is-this-loop-faster-than-a-dictionary-comprehension-for-creating-a-dictionar – RomanPerekhrest Oct 16 '19 at 10:44

score 2 · Accepted Answer · answered Oct 16 '19 at 10:33

2

Yes, at least one: Comprehensions

user_mapping = { user['id']:user['member_name'] for user in users['team'] }

comprehensions are both faster and more pythonic than for loops

answered Oct 16 '19 at 10:33

GPhilo

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What is a more efficient way to extract sub-dicts from a list of dicts in python?

2 Answers2