[Python][Google App Engine][Twitter][OAuth]access token

前回、昔、書いた[Google App Engine][twitter][oauth]ログインを自作するから少し仕様が変わったみたいで、少し見やすくして、新しくクラスを作ってみたのですが、アクセストークンを取得するメソッドを追加しました。
#twitter.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-
#
# Copyright 2007 Google Inc.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#

from google.appengine.api import urlfetch
import datetime
import time
import random
import urllib
import hmac
import hashlib
import logging

#class SignInWithTwitter(object):

class LoginTwitter(object):
    def __init__(self,consumer_secret,consumer_key):
        self.consumer_secret = consumer_secret
        self.access_token_secret = ""
        self.method = "POST"


        self.request_token_url = "https://api.twitter.com/oauth/request_token"
        self.oauth_authenticate_url = "https://api.twitter.com/oauth/authenticate?oauth_token="
        self.access_token_url = "https://api.twitter.com/oauth/access_token"

        self.prms = {
            "oauth_consumer_key":consumer_key,
            "oauth_nonce":LoginTwitter._nonce(),
            "oauth_signature_method":'HMAC-SHA1',
            "oauth_version":'1.0',
            "oauth_timestamp":LoginTwitter._timeStamp()
        }

    def getOauthToken(self):
        if self.prms.has_key("oauth_token"):
            return self.prms["oauth_token"]
        else:
            return None

    def setOauthCallbackUrl(self,oauth_callback_url):
        self.prms["oauth_callback"] = oauth_callback_url

    def setOauthToken(self,oauth_token):
        self.prms["oauth_token"] = oauth_token

    def getRedirectOauthAuthenticateUrl(self):
        if self.prms.has_key("oauth_token"):
            _url = self.oauth_authenticate_url + self.prms["oauth_token"]
            return _url
        else:
            return None


    @classmethod
    def _timeStamp(cls):
        _d = datetime.datetime.today()
        _d = time.mktime(_d.timetuple())
        _d = str(int(_d))
        return _d

    @classmethod
    def _nonce(cls):
        _s = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz123456789[]{}!$%&'()-^\:;*+><"
        _l = list(_s)
        _n = ""
        for i in range(20):
            _x = random.randint(0,len(_l)-1)
            _n += _l[_x]
        return _n

    def _signature(self,request_url):
        _prms_keys = sorted(self.prms.keys())
        _prms = ''
        for i in _prms_keys:
            _prms = _prms + "&" + i + "=" + urllib.quote_plus(self.prms[i])
        else:
            _prms = _prms[1:]

        _prms = urllib.quote_plus(self.method) + "&" + urllib.quote_plus(request_url) + "&" + urllib.quote_plus(_prms)
        _h = hmac.new("%s&%s" % (urllib.quote(self.consumer_secret), urllib.quote(self.access_token_secret)), _prms, hashlib.sha1)
        _sig = _h.digest().encode("base64").strip()
        return _sig

    def requestAccessToken(self,oauth_verifier):
        _response = self._request(self.access_token_url,{"oauth_verifier":oauth_verifier})
        return _response

    def requestOAuthToken(self):
        _response = self._request(self.request_token_url,{"oauth_callback":self.prms["oauth_callback"]})
        if _response is None:
            return False

        if _response["oauth_callback_confirmed"] == "true":
            self.prms["oauth_token"] = _response["oauth_token"]
            return True
        else:
            return False

    def _request(self,request_url,request_prms):
        self.prms['oauth_signature'] = self._signature(request_url)

        if self.method == 'POST':
            _headers = {
                'Content-Type': 'application/x-www-form-urlencoded'
            }

            _prms_keys = sorted(self.prms.keys())
            _prms = ''
            for i in _prms_keys:
                _prms = _prms + "," + i + "=\"" + urllib.quote_plus(self.prms[i]) + "\""
            else:
                _prms = _prms[1:]

            _prms = "OAuth " + _prms
            _headers["Authorization"] = _prms
            _result = urlfetch.fetch(
                url = request_url,
                payload = urllib.urlencode(request_prms),
                method = urlfetch.POST,
                headers = _headers
            )
            logging.info(_result.status_code)
            logging.info(_result.content)
            if _result.status_code == 200:
                _content = _result.content
                _content = _content.split("&")
                _response = {}
                for i in _content:
                    key_value = i.split("=")
                    _response[key_value[0]] = key_value[1]
                return _response

            else:
                return None