force.com REST API OAuth fails on POST request ?

[Ghalame]

I am using REST API for OAuth implementation from python, I am able to get the access token from refresh token, But unable to perform POST call for updating the records it give "Bad request" error.

The access Token is in Unicode so I have converter it to String. 

Please refer the below code:

def standardRequestCreate(self, url, data, accessToken):

    request = urllib2.Request(url)
    request.add_header('Authorization','OAuth '+str(accessToken))  //"OAuth " sting appends to token
    request.add_header('Content-type','application/json')
    request.add_data(data)
    jsonResponse = urllib2.urlopen(request)

    return jsonResponse

How to implement POST call as its working for my GET request.