CODEWITHSUNDEEP
pythonlistsortingdictionary
Francisco Castro
Francisco Castro

Reputation: 11

How to sort a list of dictionaries by the value of a key and by the value of a value of a key?

{
    "states": [
        {
            "timestamp": {
                "double": 968628281.0
            },
            "sensorSerialNumber": 13020235
        },
        {
            "timestamp": {
                "double": 964069109.0
            },
            "sensorSerialNumber": 13020203
        },
        {
            "timestamp": {
                "double": 9641066.0
            },
            "sensorSerialNumber": 30785
        }
    ]
}

Is there a way to sort this list of dictionaries by "sensorSerialNumber" and by this number inside the value of "timestamp" (9.68628281E8),

"timestamp":{"double":9.68628281E8}

using the built-in function(sorted)

from operator import itemgetter
newlist = sorted(list_to_be_sorted, key=itemgetter('name'))

However, my question is slightly different from other questions. If there wasn't a dictionary inside the dictionary I would just need to add the string of the second key to the built-in function, like:

from operator import itemgetter
newlist = sorted(list_to_be_sorted, key=itemgetter('name', 'age'))

Upvotes: 1

Views: 62

Answers (1)

Martijn Pieters
Martijn Pieters

Reputation: 1121406

key can be any callable, it is passed each element in the list_to_be_sorted in turn. So a lambda would fit here:

newlist = sorted(
    data['states'],
    key=lambda i: (i['sensorSerialNumber'], i['timestamp']['double']))

So the lambda returns the value for the 'sensorSerialNumber' key as the first element of a tuple, and the value for the 'double' key from the dictionary value for the 'timestamp' key.

Demo:

>>> data = {"states" :
... [{"timestamp":{"double":9.68628281E8},"sensorSerialNumber":13020235},
... {"timestamp":{"double":9.64069109E8},"sensorSerialNumber":13020203},
... {"timestamp":{"double":9641066.0},"sensorSerialNumber":30785}]
... }
>>> sorted(data['states'], key=lambda i: (i['sensorSerialNumber'], i['timestamp']['double']))
[{'timestamp': {'double': 9641066.0}, 'sensorSerialNumber': 30785}, {'timestamp': {'double': 964069109.0}, 'sensorSerialNumber': 13020203}, {'timestamp': {'double': 968628281.0}, 'sensorSerialNumber': 13020235}]
>>> from pprint import pprint
>>> pprint(_)
[{'sensorSerialNumber': 30785, 'timestamp': {'double': 9641066.0}},
 {'sensorSerialNumber': 13020203, 'timestamp': {'double': 964069109.0}},
 {'sensorSerialNumber': 13020235, 'timestamp': {'double': 968628281.0}}]

The demo is not that meaningful, as there are no equal serial numbers for the inclusion of the timestamp value to make a difference.

Upvotes: 2

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