sorting list of nested dictionaries in python

Question

I have something like

[
    {
        "key": { "subkey1":1, "subkey2":"a"  }
    },
    {
        "key": { "subkey1":10, "subkey2":"b" }
    },
    {
        "key": { "subkey1":5, "subkey2":"c" }
    }
]

And would need to have :

[
    {
        "key": { "subkey1":10, "subkey2":"b" }
    },
    {
        "key": { "subkey1":5, "subkey2":"c" }
    },
    {
        "key": { "subkey1":1, "subkey2":"a" }
    }
]

Many thanks!

EDIT : I'd like to sort by subkey1, this wasn't clear previously.

Martijn Pieters · Accepted Answer · 2012-11-05 18:27:16Z

21

Use the key keyword to the sorted() function and sort() method:

yourdata.sort(key=lambda e: e['key']['subkey'], reverse=True)

Demo:

>>> yourdata = [{'key': {'subkey': 1}}, {'key': {'subkey': 10}}, {'key': {'subkey': 5}}]
>>> yourdata.sort(key=lambda e: e['key']['subkey'], reverse=True)
>>> yourdata
[{'key': {'subkey': 10}}, {'key': {'subkey': 5}}, {'key': {'subkey': 1}}]

This assumes that all top-level dictionaries have a key key, which is assumed to be a dictionary with a subkey key.

See the Python Sorting HOWTO for more details and tricks.

edited Nov 5, 2012 at 18:27

answered Nov 5, 2012 at 18:19

Martijn Pieters

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Comments

Platinum Azure · Accepted Answer · 2012-11-05 18:20:27Z

3

Assuming you want to sort by the value of d['key']['subkey'] for every dictionary d in the list, use this:

sorted(yourdata, key=lambda d: d.get('key', {}).get('subkey'), reverse=True)

answered Nov 5, 2012 at 18:20

Platinum Azure

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1 Comment

Ezio Over a year ago

Thanks so much for your answer, it worked on a very complex nested dictionaries list. Take a bow!

alexvassel · Accepted Answer · 2012-11-05 18:17:53Z

-2

sorted(yourdata, reverse=True)

answered Nov 5, 2012 at 18:17

alexvassel

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4 Comments

Jon Clements Over a year ago

I didn't downvote this, but you'll realise that a dict as an iterable returns the keys, so you won't end up with a useful list

alexvassel Over a year ago

did not understand. the output just like asked.

Martijn Pieters Over a year ago

@alexvassel: The output in the simple example case happens to be the same, but if any of the dictionaries has an extra key in it, the results will be very different indeed. I didn't downvote your answer, but it is incorrect on that account.

Jon Clements Over a year ago

What happens sometimes is that the question changes, although it's a valid answer in some sense... I just wouldn't worry about it... ie: you post a working solution, and then all of a sudden the question changes... and your solution doesn't work... Some people will downvote on the slightest off and others will comment that it's not workable and why (I prefer the latter)...

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