In Python, how do I sort an array of JSON objects by a value in each object?

Question

I'm using Python 3.7. I have an array of JSON objects. I would like to sort the array of objects based on one of the values ("score") in each JOSN object. I'm having trouble figuring out how to write the sort function. I tried this

>>> arr = [{'score': 10, 'name': 'Bob'}, {'score': 15, 'name':'Susan'}, {'score': 1, 'name': 'Skippy'}]
>>> arr
[{'score': 10, 'name': 'Bob'}, {'score': 15, 'name': 'Susan'}, {'score': 1, 'name': 'Skippy'}]
>>> arr.sort(key=json['score'], reverse=True)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'json' is not defined
>>> arr.sort(key=json['score'], reverse=True)

but I can't figure out how to reference the JSON object from the "key" part of the sort function.

Djaouad · Accepted Answer · 2021-02-11 13:16:04Z

5

Use either a lambda function (with a parameter named json or whatever):

arr.sort(key = lambda json: json['score'], reverse=True)

Or, operator.itemgetter:

from operator import itemgetter

arr.sort(key = itemgetter('score'), reverse=True)

edited Feb 11, 2021 at 13:16

answered Aug 29, 2019 at 16:41

Djaouad

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m_____z · Accepted Answer · 2019-08-29 16:40:27Z

3

You can use sorted(iterable, key) and itemgetter as follows:

>>> from operator import itemgetter
>>> arr = [{'score': 10, 'name': 'Bob'}, {'score': 15, 'name':'Susan'}, {'score': 1, 'name': 'Skippy'}]
>>> sorted(arr, key=itemgetter('score'), reverse=True)
[{'score': 15, 'name': 'Susan'}, {'score': 10, 'name': 'Bob'}, {'score': 1, 'name': 'Skippy'}]

itemgetter('score') allows sorted to access the key element in of each dictionary in your list of dictionaries and order the list accordingly.

answered Aug 29, 2019 at 16:40

m_____z

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