List of values for a key in List of list of dictionaries?

Question

Suppose I have a list of a list of dictionaries.

I'm pretty sure Python has a nice and short way (without writing 2 for loops) to retrieve the value associated with the key. (Every dictionary has a key).

How can I do this?

Edit : There is a sample (JSON representation) of the input

[
    [
        {
            "lat": 45.1845931, 
            "lgt": 5.7316984, 
            "name": "Chavant", 
            "sens": "", 
            "line" : [],
            "stationID" : ""
        }, 
        {
            "lat": 45.1845898, 
            "lgt": 5.731746, 
            "name": "Chavant", 
            "sens": "", 
            "line" : [],
            "stationID" : ""
        }
    ], 
    [
        {
            "lat": 45.1868233, 
            "lgt": 5.7565727, 
            "name": "Neyrpic - Belledonne", 
            "sens": "", 
            "line" : [],
            "stationID" : ""
        }, 
        {
            "lat": 45.1867322, 
            "lgt": 5.7568569, 
            "name": "Neyrpic - Belledonne", 
            "sens": "", 
            "line" : [],
            "stationID" : ""
        }
    ]
]

As output I'd like to have a list of names.

PS: Data under ODBL.

Please provide a sample input and output. – tobias_k Jan 30 '14 at 21:26 — tobias_k, Jan 30 '14 at 21:26

ndpu · Accepted Answer · 2014-01-30T21:34:37.390

2

If you need all names in flat list:

response = # your big list
[d.get('name') for lst in response for d in lst]

if you want to get result with inner list:

[[d.get('name') for d in lst] for lst in response]

edited Jan 30 '14 at 21:34

answered Jan 30 '14 at 21:29

ndpu

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This will also flatten the nested list. Not sure from the question whether this is intended. – tobias_k Jan 30 '14 at 21:30
well I was also interested into doing this. So yes. – Matthieu Riegler Jan 30 '14 at 21:34

score 1 · Answer 2 · answered Jan 30 '14 at 21:30

Call your list of lists of dictionaries L. Then you can retrieve all names using a list comprehension by iterating through each sublist and then each dictionary.

Demo

>>> vals = [ d['name'] for sublist in L for d in sublist ]
>>> vals
[u'Chavant', u'Chavant', u'Neyrpic - Belledonne', u'Neyrpic - Belledonne']

Note that this returns a flattened list of all names (and that 'Chavant' appears twice, since it appears twice in your input).

List of values for a key in List of list of dictionaries?

2 Answers2

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