[python] urllib2 and json

can anyone point out a tutorial that shows me how to do a POST request using urllib2 with the data being in JSON format?

You certainly want to hack the header to have a proper Ajax Request :

headers = {'X_REQUESTED_WITH' :'XMLHttpRequest',
           'ACCEPT': 'application/json, text/javascript, */*; q=0.01',}
request = urllib2.Request(path, data, headers)
response = urllib2.urlopen(request).read()

And to json.loads the POST on the server-side.

Edit : By the way, you have to urllib.urlencode(mydata_dict) before sending them. If you don't, the POST won't be what the server expect

Example - sending some data encoded as JSON as a POST data:

import json
import urllib2
data = json.dumps([1, 2, 3])
f = urllib2.urlopen(url, data)
response = f.read()
f.close()

Whatever urllib is using to figure out Content-Length seems to get confused by json, so you have to calculate that yourself.

import json
import urllib2
data = json.dumps([1, 2, 3])
clen = len(data)
req = urllib2.Request(url, data, {'Content-Type': 'application/json', 'Content-Length': clen})
f = urllib2.urlopen(req)
response = f.read()
f.close()

Took me for ever to figure this out, so I hope it helps someone else.

This is what worked for me:

import json
import requests
url = 'http://xxx.com'
payload = {'param': '1', 'data': '2', 'field': '4'}
headers = {'content-type': 'application/json'}
r = requests.post(url, data = json.dumps(payload), headers = headers)

Messa's answer only works if the server isn't bothering to check the content-type header. You'll need to specify a content-type header if you want it to really work. Here's Messa's answer modified to include a content-type header:

import json
import urllib2
data = json.dumps([1, 2, 3])
req = urllib2.Request(url, data, {'Content-Type': 'application/json'})
f = urllib2.urlopen(req)
response = f.read()
f.close()

To read json response use json.loads(). Here is the sample.

import json
import urllib
import urllib2

post_params = {
    'foo' : bar
}

params = urllib.urlencode(post_params)
response = urllib2.urlopen(url, params)
json_response = json.loads(response.read())