Find a value in a list of dicts

Question

Let:

M = [{'name': 'john', 'result': 12}, 
     {'name': 'sara', 'result': 20}, 
     {'name': 'karl', 'result': 11}]

If I want to find Sara's result, I thought about:

 M[[m['name'] for m in M].index('sara')]['result']     # hard to read, but works

and

[m['result'] for m in M if m['name'] == 'sara'][0]     # better

Is there an even more natural way to do this in Python?

score 3 · Accepted Answer · answered May 05 '18 at 09:43

3

Use a generator with next().

next(m['result'] for m in L if m['name'] == 'sara')

answered May 05 '18 at 09:43

Daniel Roseman

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Just to be sure to understand, this is to avoid `[...][0]`, is it a better practice? – Basj May 05 '18 at 09:45
Yes - the advantage is that it stops iterating as soon as a match is found, and doesn't construct an unnecessary list. – Daniel Roseman May 05 '18 at 09:47
1

add a default `None` second parameter to return `None` instead of `StopIteration` exception – Jean-François Fabre May 05 '18 at 09:51

score 3 · Answer 2 · answered May 05 '18 at 09:50

If you have several lookups to perform, linear search isn't the best option.

Rebuild a dictionary once with the proper key (name):

M = [{'name': 'john', 'result': 12},
     {'name': 'sara', 'result': 20},
     {'name': 'karl', 'result': 11}]

newdict = {d["name"] : d["result"] for d in M}

It creates:

{'john': 12, 'karl': 11, 'sara': 20}

now when you need the result from a name, just do:

print(newdict.get('sara'))

Find a value in a list of dicts

2 Answers2