How do I send a POST request as a JSON?

data = {
        'ids': [12, 3, 4, 5, 6 , ...]
    }
    urllib2.urlopen("http://abc.com/api/posts/create",urllib.urlencode(data))

I want to send a POST request, but one of the fields should be a list of numbers. How can I do that ? (JSON?)

If your server is expecting the POST request to be json, then you would need to add a header, and also serialize the data for your request...

Python 2.x

import json
import urllib2

data = {
        'ids': [12, 3, 4, 5, 6]
}

req = urllib2.Request('http://example.com/api/posts/create')
req.add_header('Content-Type', 'application/json')

response = urllib2.urlopen(req, json.dumps(data))

Python 3.x

https://stackoverflow.com/a/26876308/496445

If you don't specify the header, it will be the default application/x-www-form-urlencoded type.

I recommend using the incredible requests module.

http://docs.python-requests.org/en/v0.10.7/user/quickstart/#custom-headers

url = 'https://api.github.com/some/endpoint'
payload = {'some': 'data'}
headers = {'content-type': 'application/json'}

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

for python 3.4.2 I found the following will work:

import urllib.request
import json

body = {'ids': [12, 14, 50]}
myurl = "http://www.testmycode.com"

req = urllib.request.Request(myurl)
req.add_header('Content-Type', 'application/json; charset=utf-8')
jsondata = json.dumps(body)
jsondataasbytes = jsondata.encode('utf-8')   # needs to be bytes
req.add_header('Content-Length', len(jsondataasbytes))
response = urllib.request.urlopen(req, jsondataasbytes)

This works perfect for Python 3.5, if the URL contains Query String / Parameter value,

Request URL = https://bah2.com/ws/rest/v1/concept/
Parameter value = 21f6bb43-98a1-419d-8f0c-8133669e40ca

import requests

url = 'https://bahbah2.com/ws/rest/v1/concept/21f6bb43-98a1-419d-8f0c-8133669e40ca'
data = {"name": "Value"}
r = requests.post(url, auth=('username', 'password'), json=data)
print(r.status_code)