JSON output sorting in Python

Question

I've a problem with JSON in python.

In fact, if I try to execute this code, python gives me a sorted JSON string!

For example:

values = {
  'profile': 'testprofile',
  'format': 'RSA_RC4_Sealed',
  'enc_key': base64.b64encode(chiave_da_inviare),
  'request': base64.b64encode(data)
}

values_json = json.dumps(values, sort_keys = False, separators = (',', ':'))

And this is the output:

{
  "profile": "testprofile",
  "enc_key": "GBWo[...]NV6w==",
  "request": "TFl[...]uYw==",
  "format": "RSA_RC4_Sealed"
}

As you can see, I tried to use "sort_keys=False" but nothing changed.

How can I stop Python sorting my JSON strings?

sort_keys is False by default. docs.python.org/3/library/json.html Which python did you use? — Joe C
– Joe C, Commented Nov 4, 2018 at 5:03
As others have noticed, this example output is also un-sorted, just differently than the input example. One of the "features"of hash maps (what Python calls a dict type) is that key order doesn't matter. Output ordering is considered cosmetic. Code logic relying on order is often considered pathological. — MarkHu
– MarkHu, Commented Mar 31, 2020 at 17:37
Almost duplicate of python - Can I get JSON to load into an OrderedDict? - Stack Overflow — user202729
– user202729, Commented Nov 4, 2020 at 14:01

Tautvydas · Accepted Answer · 2015-08-04 12:53:10Z

114

Try OrderedDict from the standard library collections:

>>> import json
>>> from collections import OrderedDict
>>> values = OrderedDict([('profile','testprofile'), 
                          ('format', 'RSA_RC4_Sealed'), 
                          ('enc_key', '...'), 
                          ('request', '...')])
>>> json.dumps(values, sort_keys=False)
'{"profile": "testprofile", "format": "RSA_RC4_Sealed", "enc_key": "...", "request": "..."}'

Unfortunately this feature is New in version 2.7 for collections

edited Aug 4, 2015 at 12:53

Tautvydas

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answered May 23, 2012 at 12:44

MrGray

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3 Comments

mloskot Over a year ago

+1 for providing simple yet direct answer to the question asked

chirale Over a year ago

This feature is available to older version of Python using pip install ordereddict and then changing the import line into from ordereddict import OrderedDict as stated on this answer (tested on Python 2.6.6).

Mario Ruggier Over a year ago

Nice... but note, surprisingly, while this works for json 2.0.9 it does not work (i.e. order is not preserved in serialization) with simplejson 2.0.9 (that is supposedly just the externally installed version of json?!). Python version is 2.7.3.

Michael come lately · Accepted Answer · 2020-01-06 22:13:23Z

55

You are storing your values into a Python dict which has no inherent notion of ordering at all, it's just a key-to-value map. So your items lose all ordering when you place them into the values variable.

In fact the only way to get a deterministic ordering would be to use sort_keys=True, which I assume places them in alphanumeric ordering. Why is the order so important?

edited Jan 6, 2020 at 22:13

Michael come lately

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answered May 5, 2010 at 15:06

Joseph Lisee

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6 Comments

elledienne Over a year ago

because i think that my code doesn't work because the order is not the right. is it possible?

Joseph Lisee Over a year ago

You code is working fine, its just that the order is undefined. If you want to always be consistent use "sort_keys=True".

Raunak Dugar Over a year ago

what if i want to sort by values rather than keys ?

iAdjunct Over a year ago

There is at least one very-valid reason to want to sort these: if you want to hash the dictionary to quickly determine later if a dictionary is identical but can't store the original dictionary, you need a deterministic representation of the dictionary.

user202729 Over a year ago

Note that since Python 3.7, dict remembers their insertion order by default.

|

innov8 · Accepted Answer · 2016-09-29 07:53:55Z

An OrderedDict as discussed elsewhere is most of the solution to your problem, and an 'ObjDict' could be even better.

However if you need the order maintained on loading, then you will also need the json.loads() to load the values into an OrderedDict. To do this use

from collections import OrderedDict
values=json.loads(jsontext,object_pairs_hook=OrderedDict)

Otherwise even though the json file will be in order, that order will be lost when loaded.

Perhaps an even better solution is to use 'ObjDict' in place of OrderedDict. This requires a pip install objdict. ObjDict still maintains order, as with OrderedDict, but also brings JSON support and better handling of this example.

from objdict import ObjDict
values = ObjDict("""{"profile" : "testprofile",
      "format": "RSA_RC4_Sealed" }""")
values.enc_key = base64.b64encode(chiave_da_inviare)
values.request = base64.b64encode(data)

values_json = values.dumps(separators=(',', ':'))

Eli Courtwright · Accepted Answer · 2010-05-05 15:08:14Z

10

If you specify sort_keys=False then Python will simply print the items in whatever order they appear in the underlying Python dict object. In some cases this may happen to be the same as the default alphanumeric sort order. In your example, the keys AREN'T even sorted like that, since "format" comes after "request". Regardless, the sort_keys parameter is still valid, as evidenced by this sample code:

>>> import json
>>> json.dumps({"a":5, "b":6, "c":7}, sort_keys=False)
'{"a": 5, "c": 7, "b": 6}'

answered May 5, 2010 at 15:08

Eli Courtwright

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Comments

Community · Accepted Answer · 2020-03-09 16:20:54Z

10

You can sort json data using simple json.dumps as

sorted_json = json.dumps(values, sort_keys=True)

If you want no need to sort simply provide

unsorted_json = json.dumps(values)

or:

unsorted_json = json.dumps(values, sort_keys=False)

edited Mar 9, 2020 at 16:20

CommunityBot

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answered Jul 19, 2018 at 10:47

Praveen

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Comments

Ned Batchelder · Accepted Answer · 2010-05-05 15:06:01Z

5

The keys aren't sorted: "profile", "enc_key", "request", "format".

It sounds like you want them to appear in the same order that you created them in the dictionary, but dictionaries are inherently unsorted, they don't remember the order you inserted keys.

There are a number of SortedDict implementations that you can use, but the json encoder won't know to use it to get the keys in the order you want.

answered May 5, 2010 at 15:06

Ned Batchelder

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