Python Requests module JSON format

Question

I have a Django application with tastypie set up for REST.

I want to be able to update the database using the REST API.

I can issue a curl command on the command line to achive what I want, (as per the tastypie documentation).

curl --dump-header - -H "Content-Type: application/json" -X PATCH --data '{"comments": "comment1"}' http://127.0.0.1:8000/api/seq/loadedwith/12092/

HTTP/1.0 202 ACCEPTED
Date: Fri, 26 Oct 2012 11:06:58 GMT
Server: WSGIServer/0.1 Python/2.6.6
Content-Type: text/html; charset=utf-8

So now I am trying to achieve the same thing using the requests module. Get requests work from the python requests module, but I can't get patch or posts to work.

url='http://127.0.0.1:8000/api/seq/loadedwith/12092/'
headers={'content-type': 'application/json'}
payload={"comments":"comment2"}
requests.patch(url=url, params=json.dumps(payload),  headers=headers)

I get the error:

  File "<stdin>", line 1, in <module>
  File "/usr/local/lib/python2.7/dist-packages/requests-0.14.1-py2.7.egg/requests/api.py", line 120, in patch
      return request('patch', url,  data=data, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/requests-0.14.1-py2.7.egg/requests/safe_mode.py", line 39, in wrapped
      return function(method, url, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/requests-0.14.1-py2.7.egg/requests/api.py", line 51, in request
      return session.request(method=method, url=url, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/requests-0.14.1-py2.7.egg/requests/sessions.py", line 182, in request
    params=from_key_val_list(params),
  File "/usr/local/lib/python2.7/dist-packages/requests-0.14.1-py2.7.egg/requests/utils.py", line 135, in from_key_val_list
    raise ValueError('cannot encode objects that are not 2-tuples')
ValueError: cannot encode objects that are not 2-tuples

This seems to be coming when I add the json.dumps(payload) - I tried passing just the dictionary, but the payload gets added to the querysting in that case, and tastypie complains. I have tried formatting the dictionary as a tuple , but I am not sure what it expects exactly.

Can someone help, (or am I looking at the wrong place in the code)?

Answer 1

params should always be a dict or a sequence of 2-value tuples, which are then encoded for you. You, however, want to upload an already encoded body, so you want the data keyword instead:

requests.patch(url, data=json.dumps(payload), headers=headers)

In fact, data is the second parameter, so you could even do:

requests.patch(url, json.dumps(payload), headers=headers)

as you normally only send opaque data with PATCH. The .post() and .put() methods behave in the same way, the second parameter is the data keyword.