Items in JSON object are out of order using json dumps

Question

I m using json dumps to convert into json like  countries append   id  row id  name  row name  timezone  row timezone   print json dumps countries    The result i have is          timezone   4   id   1   name    Mauritius          timezone   2   id   2   name    France          timezone   1   id   3   name    England          timezone   -4   id   4   name    USA       I want to have the keys in the following order  id  name  timezone - but instead I have timezone  id  name   How should I fix this

User · Answer

As others have mentioned the underlying dict is unordered. However there are OrderedDict objects in python. ( They're built in in recent pythons, or you can use this: http://code.activestate.com/recipes/576693/ ).

I believe that newer pythons json implementations correctly handle the built in OrderedDicts, but I'm not sure (and I don't have easy access to test).

Old pythons simplejson implementations dont handle the OrderedDict objects nicely .. and convert them to regular dicts before outputting them.. but you can overcome this by doing the following:

class OrderedJsonEncoder( simplejson.JSONEncoder ):
   def encode(self,o):
      if isinstance(o,OrderedDict.OrderedDict):
         return "{" + ",".join( [ self.encode(k)+":"+self.encode(v) for (k,v) in o.iteritems() ] ) + "}"
      else:
         return simplejson.JSONEncoder.encode(self, o)

now using this we get:

>>> import OrderedDict
>>> unordered={"id":123,"name":"a_name","timezone":"tz"}
>>> ordered = OrderedDict.OrderedDict( [("id",123), ("name","a_name"), ("timezone","tz")] )
>>> e = OrderedJsonEncoder()
>>> print e.encode( unordered )
{"timezone": "tz", "id": 123, "name": "a_name"}
>>> print e.encode( ordered )
{"id":123,"name":"a_name","timezone":"tz"}

Which is pretty much as desired.

Another alternative would be to specialise the encoder to directly use your row class, and then you'd not need any intermediate dict or UnorderedDict.

User · Answer

Both Python dict  before Python 3 7  and JSON object are unordered collections  You could pass sort keys parameter  to sort the keys    gt  gt  gt  import json  gt  gt  gt  json dumps   a   1   b   2      b   2   a   1    gt  gt  gt  json dumps   a   1   b   2   sort keys True     a   1   b   2     If you need a particular order  you could use collections OrderedDict    gt  gt  gt  from collections import OrderedDict  gt  gt  gt  json dumps OrderedDict    a   1     b   2        a   1   b   2    gt  gt  gt  json dumps OrderedDict    b   2     a   1        b   2   a   1     Since Python 3 6  the keyword argument order is preserved and the above can be rewritten using a nicer syntax    gt  gt  gt  json dumps OrderedDict a 1  b 2      a   1   b   2    gt  gt  gt  json dumps OrderedDict b 2  a 1      b   2   a   1     See PEP 468     Preserving Keyword Argument Order   If your input is given as JSON then to preserve the order  to get OrderedDict   you could pass object pair hook   as suggested by  Fred Yankowski    gt  gt  gt  json loads    a   1   b   2    object pairs hook OrderedDict  OrderedDict    a   1     b   2     gt  gt  gt  json loads    b   2   a   1    object pairs hook OrderedDict  OrderedDict    b   2     a   1

User · Answer

json dump   will preserve the ordder of your dictionary  Open the file in a text editor and you will see  It will preserve the order regardless of whether you send it an OrderedDict   But json load   will lose the order of the saved object unless you tell it to load into an OrderedDict    which is done with the object pairs hook parameter as J F Sebastian instructed above   It would otherwise lose the order because under usual operation  it loads the saved dictionary object into a regular dict and a regular dict does not preserve the oder of the items it is given

User · Answer

hey i know it is so late for this answer but add sort keys and assign false to it as follows    json dumps               sort keys False    this worked for me

User · Answer

in JSON  as in Javascript  order of object keys is meaningless  so it really doesn t matter what order they re displayed in  it is the same object

User · Answer

The order of a dictionary doesn t have any relationship to the order it was defined in  This is true of all dictionaries  not just those turned into JSON    gt  gt  gt    b   1   a   2    a   2   b   1    Indeed  the dictionary was turned  upside down  before it even reached json dumps    gt  gt  gt    id  1  name   David   timezone  3    timezone   3   id   1   name    David

[python] Items in JSON object are out of order using "json.dumps"?

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