SfApi.py

from suds.client import Client
from suds.sax.element import Element
url = "file:///home/jitendra/obs/wsdl.jsp.xml"
client = Client(url)
token = "xxxxxxxxxxxxxxxxxxxxxxxx"
print client

LoginResult = client.service.login("userId", "pwd"+token)

#Specifies the server URL as the target for subsequent service requests. The login server supports only login calls.
client.wsdl.services[0].setlocation(LoginResult.serverUrl)

#Sets the session ID in the SOAP header so that the API can validate subsequent requests for this session.
ssnp = Element("xsi:SessionHeader").append(Element('xsi:sessionId').setText(LoginResult.sessionId))
client.set_options(soapheaders=ssnp)

LogOutResult = client.service.logout()

print LoginResult
print client.last_sent()
print client.last_received()

Well, I didn't know that I could achieve the same thing in lesser lines of code.

svc = pyforce.PythonClient(serverUrl='https://test.salesforce.com/services/Soap/u/20.0')
LoginResult = svc.login(username='mysandboxusername', passwd='mypassword')
svc.logout()