twitter.py

#!/usr/bin/python
#
# Copyright 2007 Google Inc. All Rights Reserved.
#
# 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.

'''A library that provides a python interface to the Twitter API'''

__author__ = 'dewitt@google.com'
__version__ = '0.6-devel'


import base64
import calendar
import md5
import os
import rfc822
import sys
import tempfile
import time
import urllib
import urllib2
import urlparse

import simplejson

class TwitterError(Exception):
  '''Base class for Twitter errors'''


class Status(object):
  '''A class representing the Status structure used by the twitter API.

  The Status structure exposes the following properties:

    status.created_at
    status.created_at_in_seconds # read only
    status.favorited
    status.in_reply_to_screen_name
    status.in_reply_to_user_id
    status.in_reply_to_status_id
    status.truncated
    status.source
    status.id
    status.text
    status.relative_created_at # read only
    status.user
  '''
  def __init__(self,
               created_at=None,
               favorited=None,
               id=None,
               text=None,
               user=None,
               in_reply_to_screen_name=None,
               in_reply_to_user_id=None,
               in_reply_to_status_id=None,
               truncated=None,
               source=None,
               now=None):
    '''An object to hold a Twitter status message.

    This class is normally instantiated by the twitter.Api class and
    returned in a sequence.

    Note: Dates are posted in the form "Sat Jan 27 04:17:38 +0000 2007"

    Args:
      created_at: The time this status message was posted
      favorited: Whether this is a favorite of the authenticated user
      id: The unique id of this status message
      text: The text of this status message
      relative_created_at:
        A human readable string representing the posting time
      user:
        A twitter.User instance representing the person posting the message
      now:
        The current time, if the client choses to set it.  Defaults to the
        wall clock time.
    '''
    self.created_at = created_at
    self.favorited = favorited
    self.id = id
    self.text = text
    self.user = user
    self.now = now
    self.in_reply_to_screen_name = in_reply_to_screen_name
    self.in_reply_to_user_id = in_reply_to_user_id
    self.in_reply_to_status_id = in_reply_to_status_id
    self.truncated = truncated
    self.source = source

  def GetCreatedAt(self):
    '''Get the time this status message was posted.

    Returns:
      The time this status message was posted
    '''
    return self._created_at

  def SetCreatedAt(self, created_at):
    '''Set the time this status message was posted.

    Args:
      created_at: The time this status message was created
    '''
    self._created_at = created_at

  created_at = property(GetCreatedAt, SetCreatedAt,
                        doc='The time this status message was posted.')

  def GetCreatedAtInSeconds(self):
    '''Get the time this status message was posted, in seconds since the epoch.

    Returns:
      The time this status message was posted, in seconds since the epoch.
    '''
    return calendar.timegm(rfc822.parsedate(self.created_at))

  created_at_in_seconds = property(GetCreatedAtInSeconds,
                                   doc="The time this status message was "
                                       "posted, in seconds since the epoch")

  def GetFavorited(self):
    '''Get the favorited setting of this status message.

    Returns:
      True if this status message is favorited; False otherwise
    '''
    return self._favorited

  def SetFavorited(self, favorited):
    '''Set the favorited state of this status message.

    Args:
      favorited: boolean True/False favorited state of this status message
    '''
    self._favorited = favorited

  favorited = property(GetFavorited, SetFavorited,
                       doc='The favorited state of this status message.')

  def GetId(self):
    '''Get the unique id of this status message.

    Returns:
      The unique id of this status message
    '''
    return self._id

  def SetId(self, id):
    '''Set the unique id of this status message.

    Args:
      id: The unique id of this status message
    '''
    self._id = id

  id = property(GetId, SetId,
                doc='The unique id of this status message.')

  def GetInReplyToScreenName(self):
    return self._in_reply_to_screen_name

  def SetInReplyToScreenName(self, in_reply_to_screen_name):
    self._in_reply_to_screen_name = in_reply_to_screen_name

  in_reply_to_screen_name = property(GetInReplyToScreenName, SetInReplyToScreenName,
                doc='')

  def GetInReplyToUserId(self):
    return self._in_reply_to_user_id

  def SetInReplyToUserId(self, in_reply_to_user_id):
    self._in_reply_to_user_id = in_reply_to_user_id

  in_reply_to_user_id = property(GetInReplyToUserId, SetInReplyToUserId,
                doc='')

  def GetInReplyToStatusId(self):
    return self._in_reply_to_status_id

  def SetInReplyToStatusId(self, in_reply_to_status_id):
    self._in_reply_to_status_id = in_reply_to_status_id

  in_reply_to_status_id = property(GetInReplyToStatusId, SetInReplyToStatusId,
                doc='')

  def GetTruncated(self):
    return self._truncated

  def SetTruncated(self, truncated):
    self._truncated = truncated

  truncated = property(GetTruncated, SetTruncated,
                doc='')

  def GetSource(self):
    return self._source

  def SetSource(self, source):
    self._source = source

  source = property(GetSource, SetSource,
                doc='')

  def GetText(self):
    '''Get the text of this status message.

    Returns:
      The text of this status message.
    '''
    return self._text

  def SetText(self, text):
    '''Set the text of this status message.

    Args:
      text: The text of this status message
    '''
    self._text = text

  text = property(GetText, SetText,
                  doc='The text of this status message')

  def GetRelativeCreatedAt(self):
    '''Get a human redable string representing the posting time

    Returns:
      A human readable string representing the posting time
    '''
    fudge = 1.25
    delta  = int(self.now) - int(self.created_at_in_seconds)

    if delta < (1 * fudge):
      return 'about a second ago'
    elif delta < (60 * (1/fudge)):
      return 'about %d seconds ago' % (delta)
    elif delta < (60 * fudge):
      return 'about a minute ago'
    elif delta < (60 * 60 * (1/fudge)):
      return 'about %d minutes ago' % (delta / 60)
    elif delta < (60 * 60 * fudge):
      return 'about an hour ago'
    elif delta < (60 * 60 * 24 * (1/fudge)):
      return 'about %d hours ago' % (delta / (60 * 60))
    elif delta < (60 * 60 * 24 * fudge):
      return 'about a day ago'
    else:
      return 'about %d days ago' % (delta / (60 * 60 * 24))

  relative_created_at = property(GetRelativeCreatedAt,
                                 doc='Get a human readable string representing'
                                     'the posting time')

  def GetUser(self):
    '''Get a twitter.User reprenting the entity posting this status message.

    Returns:
      A twitter.User reprenting the entity posting this status message
    '''
    return self._user

  def SetUser(self, user):
    '''Set a twitter.User reprenting the entity posting this status message.

    Args:
      user: A twitter.User reprenting the entity posting this status message
    '''
    self._user = user

  user = property(GetUser, SetUser,
                  doc='A twitter.User reprenting the entity posting this '
                      'status message')

  def GetNow(self):
    '''Get the wallclock time for this status message.

    Used to calculate relative_created_at.  Defaults to the time
    the object was instantiated.

    Returns:
      Whatever the status instance believes the current time to be,
      in seconds since the epoch.
    '''
    if self._now is None:
      self._now = time.time()
    return self._now

  def SetNow(self, now):
    '''Set the wallclock time for this status message.

    Used to calculate relative_created_at.  Defaults to the time
    the object was instantiated.

    Args:
      now: The wallclock time for this instance.
    '''
    self._now = now

  now = property(GetNow, SetNow,
                 doc='The wallclock time for this status instance.')


  def __ne__(self, other):
    return not self.__eq__(other)

  def __eq__(self, other):
    try:
      return other and \
             self.created_at == other.created_at and \
             self.id == other.id and \
             self.text == other.text and \
             self.user == other.user and \
             self.in_reply_to_screen_name == other.in_reply_to_screen_name and \
             self.in_reply_to_user_id == other.in_reply_to_user_id and \
             self.in_reply_to_status_id == other.in_reply_to_status_id and \
             self.truncated == other.truncated and \
             self.favorited == other.favorited and \
             self.source == other.source
    except AttributeError:
      return False

  def __str__(self):
    '''A string representation of this twitter.Status instance.

    The return value is the same as the JSON string representation.

    Returns:
      A string representation of this twitter.Status instance.
    '''
    return self.AsJsonString()

  def AsJsonString(self):
    '''A JSON string representation of this twitter.Status instance.

    Returns:
      A JSON string representation of this twitter.Status instance
   '''
    return simplejson.dumps(self.AsDict(), sort_keys=True)

  def AsDict(self):
    '''A dict representation of this twitter.Status instance.

    The return value uses the same key names as the JSON representation.

    Return:
      A dict representing this twitter.Status instance
    '''
    data = {}
    if self.created_at:
      data['created_at'] = self.created_at
    if self.favorited:
      data['favorited'] = self.favorited
    if self.id:
      data['id'] = self.id
    if self.text:
      data['text'] = self.text
    if self.user:
      data['user'] = self.user.AsDict()
    if self.in_reply_to_screen_name:
      data['in_reply_to_screen_name'] = self.in_reply_to_screen_name
    if self.in_reply_to_user_id:
      data['in_reply_to_user_id'] = self.in_reply_to_user_id
    if self.in_reply_to_status_id:
      data['in_reply_to_status_id'] = self.in_reply_to_status_id
    if self.truncated is not None:
      data['truncated'] = self.truncated
    if self.favorited is not None:
      data['favorited'] = self.favorited
    if self.source:
      data['source'] = self.source
    return data

  @staticmethod
  def NewFromJsonDict(data):
    '''Create a new instance based on a JSON dict.

    Args:
      data: A JSON dict, as converted from the JSON in the twitter API
    Returns:
      A twitter.Status instance
    '''
    if 'user' in data:
      user = User.NewFromJsonDict(data['user'])
    else:
      user = None
    return Status(created_at=data.get('created_at', None),
                  favorited=data.get('favorited', None),
                  id=data.get('id', None),
                  text=data.get('text', None),
                  in_reply_to_screen_name=data.get('in_reply_to_screen_name', None),
                  in_reply_to_user_id=data.get('in_reply_to_user_id', None),
                  in_reply_to_status_id=data.get('in_reply_to_status_id', None),
                  truncated=data.get('truncated', None),
                  source=data.get('source', None),
                  user=user)


class User(object):
  '''A class representing the User structure used by the twitter API.

  The User structure exposes the following properties:

    user.id
    user.name
    user.screen_name
    user.location
    user.description
    user.profile_image_url
    user.profile_background_tile
    user.profile_background_image_url
    user.profile_sidebar_fill_color
    user.profile_background_color
    user.profile_link_color
    user.profile_text_color
    user.protected
    user.utc_offset
    user.time_zone
    user.url
    user.status
    user.statuses_count
    user.followers_count
    user.friends_count
    user.favourites_count
  '''
  def __init__(self,
               id=None,
               name=None,
               screen_name=None,
               location=None,
               description=None,
               profile_image_url=None,
               profile_background_tile=None,
               profile_background_image_url=None,
               profile_sidebar_fill_color=None,
               profile_background_color=None,
               profile_link_color=None,
               profile_text_color=None,
               protected=None,
               utc_offset=None,
               time_zone=None,
               followers_count=None,
               friends_count=None,
               statuses_count=None,
               favourites_count=None,
               url=None,
               status=None):
    self.id = id
    self.name = name
    self.screen_name = screen_name
    self.location = location
    self.description = description
    self.profile_image_url = profile_image_url
    self.profile_background_tile = profile_background_tile
    self.profile_background_image_url = profile_background_image_url
    self.profile_sidebar_fill_color = profile_sidebar_fill_color
    self.profile_background_color = profile_background_color
    self.profile_link_color = profile_link_color
    self.profile_text_color = profile_text_color
    self.protected = protected
    self.utc_offset = utc_offset
    self.time_zone = time_zone
    self.followers_count = followers_count
    self.friends_count = friends_count
    self.statuses_count = statuses_count
    self.favourites_count = favourites_count
    self.url = url
    self.status = status


  def GetId(self):
    '''Get the unique id of this user.

    Returns:
      The unique id of this user
    '''
    return self._id

  def SetId(self, id):
    '''Set the unique id of this user.

    Args:
      id: The unique id of this user.
    '''
    self._id = id

  id = property(GetId, SetId,
                doc='The unique id of this user.')

  def GetName(self):
    '''Get the real name of this user.

    Returns:
      The real name of this user
    '''
    return self._name

  def SetName(self, name):
    '''Set the real name of this user.

    Args:
      name: The real name of this user
    '''
    self._name = name

  name = property(GetName, SetName,
                  doc='The real name of this user.')

  def GetScreenName(self):
    '''Get the short username of this user.

    Returns:
      The short username of this user
    '''
    return self._screen_name

  def SetScreenName(self, screen_name):
    '''Set the short username of this user.

    Args:
      screen_name: the short username of this user
    '''
    self._screen_name = screen_name

  screen_name = property(GetScreenName, SetScreenName,
                         doc='The short username of this user.')

  def GetLocation(self):
    '''Get the geographic location of this user.

    Returns:
      The geographic location of this user
    '''
    return self._location

  def SetLocation(self, location):
    '''Set the geographic location of this user.

    Args:
      location: The geographic location of this user
    '''
    self._location = location

  location = property(GetLocation, SetLocation,
                      doc='The geographic location of this user.')

  def GetDescription(self):
    '''Get the short text description of this user.

    Returns:
      The short text description of this user
    '''
    return self._description

  def SetDescription(self, description):
    '''Set the short text description of this user.

    Args:
      description: The short text description of this user
    '''
    self._description = description

  description = property(GetDescription, SetDescription,
                         doc='The short text description of this user.')

  def GetUrl(self):
    '''Get the homepage url of this user.

    Returns:
      The homepage url of this user
    '''
    return self._url

  def SetUrl(self, url):
    '''Set the homepage url of this user.

    Args:
      url: The homepage url of this user
    '''
    self._url = url

  url = property(GetUrl, SetUrl,
                 doc='The homepage url of this user.')

  def GetProfileImageUrl(self):
    '''Get the url of the thumbnail of this user.

    Returns:
      The url of the thumbnail of this user
    '''
    return self._profile_image_url

  def SetProfileImageUrl(self, profile_image_url):
    '''Set the url of the thumbnail of this user.

    Args:
      profile_image_url: The url of the thumbnail of this user
    '''
    self._profile_image_url = profile_image_url

  profile_image_url= property(GetProfileImageUrl, SetProfileImageUrl,
                              doc='The url of the thumbnail of this user.')

  def GetProfileBackgroundTile(self):
    '''Boolean for whether to tile the profile background image.

    Returns:
      True if the background is to be tiled, False if not, None if unset.
    '''
    return self._profile_background_tile

  def SetProfileBackgroundTile(self, profile_background_tile):
    '''Set the boolean flag for whether to tile the profile background image.

    Args:
      profile_background_tile: Boolean flag for whether to tile or not.
    '''
    self._profile_background_tile = profile_background_tile

  profile_background_tile = property(GetProfileBackgroundTile, SetProfileBackgroundTile,
                                     doc='Boolean for whether to tile the background image.')

  def GetProfileBackgroundImageUrl(self):
    return self._profile_background_image_url

  def SetProfileBackgroundImageUrl(self, profile_background_image_url):
    self._profile_background_image_url = profile_background_image_url

  profile_background_image_url = property(GetProfileBackgroundImageUrl, SetProfileBackgroundImageUrl,
                                          doc='The url of the profile background of this user.')

  def GetProfileSidebarFillColor(self):
    return self._profile_sidebar_fill_color

  def SetProfileSidebarFillColor(self, profile_sidebar_fill_color):
    self._profile_sidebar_fill_color = profile_sidebar_fill_color

  profile_sidebar_fill_color = property(GetProfileSidebarFillColor, SetProfileSidebarFillColor)

  def GetProfileBackgroundColor(self):
    return self._profile_background_color

  def SetProfileBackgroundColor(self, profile_background_color):
    self._profile_background_color = profile_background_color

  profile_background_color = property(GetProfileBackgroundColor, SetProfileBackgroundColor)

  def GetProfileLinkColor(self):
    return self._profile_link_color

  def SetProfileLinkColor(self, profile_link_color):
    self._profile_link_color = profile_link_color

  profile_link_color = property(GetProfileLinkColor, SetProfileLinkColor)

  def GetProfileTextColor(self):
    return self._profile_text_color

  def SetProfileTextColor(self, profile_text_color):
    self._profile_text_color = profile_text_color

  profile_text_color = property(GetProfileTextColor, SetProfileTextColor)

  def GetProtected(self):
    return self._protected

  def SetProtected(self, protected):
    self._protected = protected

  protected = property(GetProtected, SetProtected)

  def GetUtcOffset(self):
    return self._utc_offset

  def SetUtcOffset(self, utc_offset):
    self._utc_offset = utc_offset

  utc_offset = property(GetUtcOffset, SetUtcOffset)

  def GetTimeZone(self):
    '''Returns the current time zone string for the user.

    Returns:
      The descriptive time zone string for the user.
    '''
    return self._time_zone

  def SetTimeZone(self, time_zone):
    '''Sets the user's time zone string.

    Args:
      time_zone: The descriptive time zone to assign for the user.
    '''
    self._time_zone = time_zone

  time_zone = property(GetTimeZone, SetTimeZone)

  def GetStatus(self):
    '''Get the latest twitter.Status of this user.

    Returns:
      The latest twitter.Status of this user
    '''
    return self._status

  def SetStatus(self, status):
    '''Set the latest twitter.Status of this user.

    Args:
      status: The latest twitter.Status of this user
    '''
    self._status = status

  status = property(GetStatus, SetStatus,
                  doc='The latest twitter.Status of this user.')

  def GetFriendsCount(self):
    '''Get the friend count for this user.
    
    Returns:
      The number of users this user has befriended.
    '''
    return self._friends_count

  def SetFriendsCount(self, count):
    '''Set the friend count for this user.

    Args:
      count: The number of users this user has befriended.
    '''
    self._friends_count = count

  friends_count = property(GetFriendsCount, SetFriendsCount,
                  doc='The number of friends for this user.')

  def GetFollowersCount(self):
    '''Get the follower count for this user.
    
    Returns:
      The number of users following this user.
    '''
    return self._followers_count

  def SetFollowersCount(self, count):
    '''Set the follower count for this user.

    Args:
      count: The number of users following this user.
    '''
    self._followers_count = count

  followers_count = property(GetFollowersCount, SetFollowersCount,
                  doc='The number of users following this user.')

  def GetStatusesCount(self):
    '''Get the number of status updates for this user.
    
    Returns:
      The number of status updates for this user.
    '''
    return self._statuses_count

  def SetStatusesCount(self, count):
    '''Set the status update count for this user.

    Args:
      count: The number of updates for this user.
    '''
    self._statuses_count = count

  statuses_count = property(GetStatusesCount, SetStatusesCount,
                  doc='The number of updates for this user.')

  def GetFavouritesCount(self):
    '''Get the number of favourites for this user.
    
    Returns:
      The number of favourites for this user.
    '''
    return self._favourites_count

  def SetFavouritesCount(self, count):
    '''Set the favourite count for this user.

    Args:
      count: The number of favourites for this user.
    '''
    self._favourites_count = count

  favourites_count = property(GetFavouritesCount, SetFavouritesCount,
                  doc='The number of favourites for this user.')

  def __ne__(self, other):
    return not self.__eq__(other)

  def __eq__(self, other):
    try:
      return other and \
             self.id == other.id and \
             self.name == other.name and \
             self.screen_name == other.screen_name and \
             self.location == other.location and \
             self.description == other.description and \
             self.profile_image_url == other.profile_image_url and \
             self.profile_background_tile == other.profile_background_tile and \
             self.profile_background_image_url == other.profile_background_image_url and \
             self.profile_sidebar_fill_color == other.profile_sidebar_fill_color and \
             self.profile_background_color == other.profile_background_color and \
             self.profile_link_color == other.profile_link_color and \
             self.profile_text_color == other.profile_text_color and \
             self.protected == other.protected and \
             self.utc_offset == other.utc_offset and \
             self.time_zone == other.time_zone and \
             self.url == other.url and \
             self.statuses_count == other.statuses_count and \
             self.followers_count == other.followers_count and \
             self.favourites_count == other.favourites_count and \
             self.friends_count == other.friends_count and \
             self.status == other.status
    except AttributeError:
      return False

  def __str__(self):
    '''A string representation of this twitter.User instance.

    The return value is the same as the JSON string representation.

    Returns:
      A string representation of this twitter.User instance.
    '''
    return self.AsJsonString()

  def AsJsonString(self):
    '''A JSON string representation of this twitter.User instance.

    Returns:
      A JSON string representation of this twitter.User instance
   '''
    return simplejson.dumps(self.AsDict(), sort_keys=True)

  def AsDict(self):
    '''A dict representation of this twitter.User instance.

    The return value uses the same key names as the JSON representation.

    Return:
      A dict representing this twitter.User instance
    '''
    data = {}
    if self.id:
      data['id'] = self.id
    if self.name:
      data['name'] = self.name
    if self.screen_name:
      data['screen_name'] = self.screen_name
    if self.location:
      data['location'] = self.location
    if self.description:
      data['description'] = self.description
    if self.profile_image_url:
      data['profile_image_url'] = self.profile_image_url
    if self.profile_background_tile is not None:
      data['profile_background_tile'] = self.profile_background_tile
    if self.profile_background_image_url:
      data['profile_sidebar_fill_color'] = self.profile_background_image_url
    if self.profile_background_color:
      data['profile_background_color'] = self.profile_background_color
    if self.profile_link_color:
      data['profile_link_color'] = self.profile_link_color
    if self.profile_text_color:
      data['profile_text_color'] = self.profile_text_color
    if self.protected is not None:
      data['protected'] = self.protected
    if self.utc_offset:
      data['utc_offset'] = self.utc_offset
    if self.time_zone:
      data['time_zone'] = self.time_zone
    if self.url:
      data['url'] = self.url
    if self.status:
      data['status'] = self.status.AsDict()
    if self.friends_count:
      data['friends_count'] = self.friends_count
    if self.followers_count:
      data['followers_count'] = self.followers_count
    if self.statuses_count:
      data['statuses_count'] = self.statuses_count
    if self.favourites_count:
      data['favourites_count'] = self.favourites_count
    return data

  @staticmethod
  def NewFromJsonDict(data):
    '''Create a new instance based on a JSON dict.

    Args:
      data: A JSON dict, as converted from the JSON in the twitter API
    Returns:
      A twitter.User instance
    '''
    if 'status' in data:
      status = Status.NewFromJsonDict(data['status'])
    else:
      status = None
    return User(id=data.get('id', None),
                name=data.get('name', None),
                screen_name=data.get('screen_name', None),
                location=data.get('location', None),
                description=data.get('description', None),
                statuses_count=data.get('statuses_count', None),
                followers_count=data.get('followers_count', None),
                favourites_count=data.get('favourites_count', None),
                friends_count=data.get('friends_count', None),
                profile_image_url=data.get('profile_image_url', None),
                profile_background_tile = data.get('profile_background_tile', None),
                profile_background_image_url = data.get('profile_background_image_url', None),
                profile_sidebar_fill_color = data.get('profile_sidebar_fill_color', None),
                profile_background_color = data.get('profile_background_color', None),
                profile_link_color = data.get('profile_link_color', None),
                profile_text_color = data.get('profile_text_color', None),
                protected = data.get('protected', None),
                utc_offset = data.get('utc_offset', None),
                time_zone = data.get('time_zone', None),
                url=data.get('url', None),
                status=status)

class DirectMessage(object):
  '''A class representing the DirectMessage structure used by the twitter API.

  The DirectMessage structure exposes the following properties:

    direct_message.id
    direct_message.created_at
    direct_message.created_at_in_seconds # read only
    direct_message.sender_id
    direct_message.sender_screen_name
    direct_message.recipient_id
    direct_message.recipient_screen_name
    direct_message.text
  '''

  def __init__(self,
               id=None,
               created_at=None,
               sender_id=None,
               sender_screen_name=None,
               recipient_id=None,
               recipient_screen_name=None,
               text=None):
    '''An object to hold a Twitter direct message.

    This class is normally instantiated by the twitter.Api class and
    returned in a sequence.

    Note: Dates are posted in the form "Sat Jan 27 04:17:38 +0000 2007"

    Args:
      id: The unique id of this direct message
      created_at: The time this direct message was posted
      sender_id: The id of the twitter user that sent this message
      sender_screen_name: The name of the twitter user that sent this message
      recipient_id: The id of the twitter that received this message
      recipient_screen_name: The name of the twitter that received this message
      text: The text of this direct message
    '''
    self.id = id
    self.created_at = created_at
    self.sender_id = sender_id
    self.sender_screen_name = sender_screen_name
    self.recipient_id = recipient_id
    self.recipient_screen_name = recipient_screen_name
    self.text = text

  def GetId(self):
    '''Get the unique id of this direct message.

    Returns:
      The unique id of this direct message
    '''
    return self._id

  def SetId(self, id):
    '''Set the unique id of this direct message.

    Args:
      id: The unique id of this direct message
    '''
    self._id = id

  id = property(GetId, SetId,
                doc='The unique id of this direct message.')

  def GetCreatedAt(self):
    '''Get the time this direct message was posted.

    Returns:
      The time this direct message was posted
    '''
    return self._created_at

  def SetCreatedAt(self, created_at):
    '''Set the time this direct message was posted.

    Args:
      created_at: The time this direct message was created
    '''
    self._created_at = created_at

  created_at = property(GetCreatedAt, SetCreatedAt,
                        doc='The time this direct message was posted.')

  def GetCreatedAtInSeconds(self):
    '''Get the time this direct message was posted, in seconds since the epoch.

    Returns:
      The time this direct message was posted, in seconds since the epoch.
    '''
    return calendar.timegm(rfc822.parsedate(self.created_at))

  created_at_in_seconds = property(GetCreatedAtInSeconds,
                                   doc="The time this direct message was "
                                       "posted, in seconds since the epoch")

  def GetSenderId(self):
    '''Get the unique sender id of this direct message.

    Returns:
      The unique sender id of this direct message
    '''
    return self._sender_id

  def SetSenderId(self, sender_id):
    '''Set the unique sender id of this direct message.

    Args:
      sender id: The unique sender id of this direct message
    '''
    self._sender_id = sender_id

  sender_id = property(GetSenderId, SetSenderId,
                doc='The unique sender id of this direct message.')

  def GetSenderScreenName(self):
    '''Get the unique sender screen name of this direct message.

    Returns:
      The unique sender screen name of this direct message
    '''
    return self._sender_screen_name

  def SetSenderScreenName(self, sender_screen_name):
    '''Set the unique sender screen name of this direct message.

    Args:
      sender_screen_name: The unique sender screen name of this direct message
    '''
    self._sender_screen_name = sender_screen_name

  sender_screen_name = property(GetSenderScreenName, SetSenderScreenName,
                doc='The unique sender screen name of this direct message.')

  def GetRecipientId(self):
    '''Get the unique recipient id of this direct message.

    Returns:
      The unique recipient id of this direct message
    '''
    return self._recipient_id

  def SetRecipientId(self, recipient_id):
    '''Set the unique recipient id of this direct message.

    Args:
      recipient id: The unique recipient id of this direct message
    '''
    self._recipient_id = recipient_id

  recipient_id = property(GetRecipientId, SetRecipientId,
                doc='The unique recipient id of this direct message.')

  def GetRecipientScreenName(self):
    '''Get the unique recipient screen name of this direct message.

    Returns:
      The unique recipient screen name of this direct message
    '''
    return self._recipient_screen_name

  def SetRecipientScreenName(self, recipient_screen_name):
    '''Set the unique recipient screen name of this direct message.

    Args:
      recipient_screen_name: The unique recipient screen name of this direct message
    '''
    self._recipient_screen_name = recipient_screen_name

  recipient_screen_name = property(GetRecipientScreenName, SetRecipientScreenName,
                doc='The unique recipient screen name of this direct message.')

  def GetText(self):
    '''Get the text of this direct message.

    Returns:
      The text of this direct message.
    '''
    return self._text

  def SetText(self, text):
    '''Set the text of this direct message.

    Args:
      text: The text of this direct message
    '''
    self._text = text

  text = property(GetText, SetText,
                  doc='The text of this direct message')

  def __ne__(self, other):
    return not self.__eq__(other)

  def __eq__(self, other):
    try:
      return other and \
          self.id == other.id and \
          self.created_at == other.created_at and \
          self.sender_id == other.sender_id and \
          self.sender_screen_name == other.sender_screen_name and \
          self.recipient_id == other.recipient_id and \
          self.recipient_screen_name == other.recipient_screen_name and \
          self.text == other.text
    except AttributeError:
      return False

  def __str__(self):
    '''A string representation of this twitter.DirectMessage instance.

    The return value is the same as the JSON string representation.

    Returns:
      A string representation of this twitter.DirectMessage instance.
    '''
    return self.AsJsonString()

  def AsJsonString(self):
    '''A JSON string representation of this twitter.DirectMessage instance.

    Returns:
      A JSON string representation of this twitter.DirectMessage instance
   '''
    return simplejson.dumps(self.AsDict(), sort_keys=True)

  def AsDict(self):
    '''A dict representation of this twitter.DirectMessage instance.

    The return value uses the same key names as the JSON representation.

    Return:
      A dict representing this twitter.DirectMessage instance
    '''
    data = {}
    if self.id:
      data['id'] = self.id
    if self.created_at:
      data['created_at'] = self.created_at
    if self.sender_id:
      data['sender_id'] = self.sender_id
    if self.sender_screen_name:
      data['sender_screen_name'] = self.sender_screen_name
    if self.recipient_id:
      data['recipient_id'] = self.recipient_id
    if self.recipient_screen_name:
      data['recipient_screen_name'] = self.recipient_screen_name
    if self.text:
      data['text'] = self.text
    return data

  @staticmethod
  def NewFromJsonDict(data):
    '''Create a new instance based on a JSON dict.

    Args:
      data: A JSON dict, as converted from the JSON in the twitter API
    Returns:
      A twitter.DirectMessage instance
    '''
    return DirectMessage(created_at=data.get('created_at', None),
                         recipient_id=data.get('recipient_id', None),
                         sender_id=data.get('sender_id', None),
                         text=data.get('text', None),
                         sender_screen_name=data.get('sender_screen_name', None),
                         id=data.get('id', None),
                         recipient_screen_name=data.get('recipient_screen_name', None))

class Api(object):
  '''A python interface into the Twitter API

  By default, the Api caches results for 1 minute.

  Example usage:

    To create an instance of the twitter.Api class, with no authentication:

      >>> import twitter
      >>> api = twitter.Api()

    To fetch the most recently posted public twitter status messages:

      >>> statuses = api.GetPublicTimeline()
      >>> print [s.user.name for s in statuses]
      [u'DeWitt', u'Kesuke Miyagi', u'ev', u'Buzz Andersen', u'Biz Stone'] #...

    To fetch a single user's public status messages, where "user" is either
    a Twitter "short name" or their user id.

      >>> statuses = api.GetUserTimeline(user)
      >>> print [s.text for s in statuses]

    To use authentication, instantiate the twitter.Api class with a
    username and password:

      >>> api = twitter.Api(username='twitter user', password='twitter pass')

    To fetch your friends (after being authenticated):

      >>> users = api.GetFriends()
      >>> print [u.name for u in users]

    To post a twitter status message (after being authenticated):

      >>> status = api.PostUpdate('I love python-twitter!')
      >>> print status.text
      I love python-twitter!

    There are many other methods, including:

      >>> api.PostDirectMessage(user, text)
      >>> api.GetUser(user)
      >>> api.GetReplies()
      >>> api.GetUserTimeline(user)
      >>> api.GetStatus(id)
      >>> api.DestroyStatus(id)
      >>> api.GetFriendsTimeline(user)
      >>> api.GetFriends(user)
      >>> api.GetFollowers()
      >>> api.GetFeatured()
      >>> api.GetDirectMessages()
      >>> api.PostDirectMessage(user, text)
      >>> api.DestroyDirectMessage(id)
      >>> api.DestroyFriendship(user)
      >>> api.CreateFriendship(user)
      >>> api.GetUserByEmail(email)
  '''

  DEFAULT_CACHE_TIMEOUT = 60 # cache for 1 minute

  _API_REALM = 'Twitter API'

  def __init__(self,
               username=None,
               password=None,
               input_encoding=None,
               request_headers=None):
    '''Instantiate a new twitter.Api object.

    Args:
      username: The username of the twitter account.  [optional]
      password: The password for the twitter account. [optional]
      input_encoding: The encoding used to encode input strings. [optional]
      request_header: A dictionary of additional HTTP request headers. [optional]
    '''
    self._cache = _FileCache()
    self._urllib = urllib2
    self._cache_timeout = Api.DEFAULT_CACHE_TIMEOUT
    self._InitializeRequestHeaders(request_headers)
    self._InitializeUserAgent()
    self._InitializeDefaultParameters()
    self._input_encoding = input_encoding
    self.SetCredentials(username, password)

  def GetPublicTimeline(self, since_id=None):
    '''Fetch the sequnce of public twitter.Status message for all users.

    Args:
      since_id:
        Returns only public statuses with an ID greater than (that is,
        more recent than) the specified ID. [Optional]

    Returns:
      An sequence of twitter.Status instances, one for each message
    '''
    parameters = {}
    if since_id:
      parameters['since_id'] = since_id
    url = 'http://twitter.com/statuses/public_timeline.json'
    json = self._FetchUrl(url,  parameters=parameters)
    data = simplejson.loads(json)
    self._CheckForTwitterError(data)
    return [Status.NewFromJsonDict(x) for x in data]

  def GetFriendsTimeline(self, user=None, since=None, since_id=None):
    '''Fetch the sequence of twitter.Status messages for a user's friends

    The twitter.Api instance must be authenticated if the user is private.

    Args:
      user:
        Specifies the ID or screen name of the user for whom to return
        the friends_timeline.  If unspecified, the username and password
        must be set in the twitter.Api instance.  [optional]
      since:
        Narrows the returned results to just those statuses created
        after the specified HTTP-formatted date. [optional]
      since_id:
        Returns only public statuses with an ID greater than (that is,
        more recent than) the specified ID. [Optional]

    Returns:
      A sequence of twitter.Status instances, one for each message
    '''
    if user:
      url = 'http://twitter.com/statuses/friends_timeline/%s.json' % user
    elif not user and not self._username:
      raise TwitterError("User must be specified if API is not authenticated.")
    else:
      url = 'http://twitter.com/statuses/friends_timeline.json'
    parameters = {}
    if since:
      parameters['since'] = since
    if since_id:
      parameters['since_id'] = since_id
    json = self._FetchUrl(url, parameters=parameters)
    data = simplejson.loads(json)
    self._CheckForTwitterError(data)
    return [Status.NewFromJsonDict(x) for x in data]

  def GetUserTimeline(self, user=None, count=None, since=None, since_id=None):
    '''Fetch the sequence of public twitter.Status messages for a single user.

    The twitter.Api instance must be authenticated if the user is private.

    Args:
      user:
        either the username (short_name) or id of the user to retrieve.  If
        not specified, then the current authenticated user is used. [optional]
      count: the number of status messages to retrieve [optional]
      since:
        Narrows the returned results to just those statuses created
        after the specified HTTP-formatted date. [optional]
      since_id:
        Returns only public statuses with an ID greater than (that is,
        more recent than) the specified ID. [Optional]

    Returns:
      A sequence of twitter.Status instances, one for each message up to count
    '''
    try:
      if count:
        int(count)
    except:
      raise TwitterError("Count must be an integer")
    parameters = {}
    if count:
      parameters['count'] = count
    if since:
      parameters['since'] = since
    if since_id:
      parameters['since_id'] = since_id
    if user:
      url = 'http://twitter.com/statuses/user_timeline/%s.json' % user
    elif not user and not self._username:
      raise TwitterError("User must be specified if API is not authenticated.")
    else:
      url = 'http://twitter.com/statuses/user_timeline.json'
    json = self._FetchUrl(url, parameters=parameters)
    data = simplejson.loads(json)
    self._CheckForTwitterError(data)
    return [Status.NewFromJsonDict(x) for x in data]

  def GetStatus(self, id):
    '''Returns a single status message.

    The twitter.Api instance must be authenticated if the status message is private.

    Args:
      id: The numerical ID of the status you're trying to retrieve.

    Returns:
      A twitter.Status instance representing that status message
    '''
    try:
      if id:
        int(id)
    except:
      raise TwitterError("id must be an integer")
    url = 'http://twitter.com/statuses/show/%s.json' % id
    json = self._FetchUrl(url)
    data = simplejson.loads(json)
    self._CheckForTwitterError(data)
    return Status.NewFromJsonDict(data)

  def DestroyStatus(self, id):
    '''Destroys the status specified by the required ID parameter.

    The twitter.Api instance must be authenticated and thee
    authenticating user must be the author of the specified status.

    Args:
      id: The numerical ID of the status you're trying to destroy.

    Returns:
      A twitter.Status instance representing the destroyed status message
    '''
    try:
      if id:
        int(id)
    except:
      raise TwitterError("id must be an integer")
    url = 'http://twitter.com/statuses/destroy/%s.json' % id
    json = self._FetchUrl(url, post_data={})
    data = simplejson.loads(json)
    self._CheckForTwitterError(data)
    return Status.NewFromJsonDict(data)

  def PostUpdate(self, text, in_reply_to_status_id=None):
    '''Post a twitter status message from the authenticated user.

    The twitter.Api instance must be authenticated.

    Args:
      text:
        The message text to be posted.  Must be less than 140 characters.
      in_reply_to_status_id:
        The ID of an existing status that the status to be posted is
        in reply to.  This implicitly sets the in_reply_to_user_id
        attribute of the resulting status to the user ID of the
        message being replied to.  Invalid/missing status IDs will be
        ignored. [Optional]

    Returns:
      A twitter.Status instance representing the message posted
    '''
    if not self._username:
      raise TwitterError("The twitter.Api instance must be authenticated.")
    if len(text) > 140:
      raise TwitterError("Text must be less than or equal to 140 characters.")
    url = 'http://twitter.com/statuses/update.json'
    data = {'status': text}
    if in_reply_to_status_id:
      data['in_reply_to_status_id'] = in_reply_to_status_id
    json = self._FetchUrl(url, post_data=data)
    data = simplejson.loads(json)
    self._CheckForTwitterError(data)
    return Status.NewFromJsonDict(data)

  def GetReplies(self, since=None, since_id=None):
    '''Get a sequence of status messages representing the 20 most recent
    replies (status updates prefixed with @username) to the authenticating
    user.

    Args:
      since:
        Narrows the returned results to just those statuses created
        after the specified HTTP-formatted date. [optional]
      since_id:
        Returns only public statuses with an ID greater than (that is,
        more recent than) the specified ID. [Optional]

    Returns:
      A sequence of twitter.Status instances, one for each reply to the user.
    '''
    url = 'http://twitter.com/statuses/replies.json'
    if not self._username:
      raise TwitterError("The twitter.Api instance must be authenticated.")
    parameters = {}
    if since:
      parameters['since'] = since
    if since_id:
      parameters['since_id'] = since_id
    json = self._FetchUrl(url, parameters=parameters)
    data = simplejson.loads(json)
    self._CheckForTwitterError(data)
    return [Status.NewFromJsonDict(x) for x in data]

  def GetFriends(self, user=None):
    '''Fetch the sequence of twitter.User instances, one for each friend.

    Args:
      user: the username or id of the user whose friends you are fetching.  If
      not specified, defaults to the authenticated user. [optional]

    The twitter.Api instance must be authenticated.

    Returns:
      A sequence of twitter.User instances, one for each friend
    '''
    if not self._username:
      raise TwitterError("twitter.Api instance must be authenticated")
    if user:
      url = 'http://twitter.com/statuses/friends/%s.json' % user
    else:
      url = 'http://twitter.com/statuses/friends.json'
    json = self._FetchUrl(url)
    data = simplejson.loads(json)
    self._CheckForTwitterError(data)
    return [User.NewFromJsonDict(x) for x in data]

  def GetFollowers(self):
    '''Fetch the sequence of twitter.User instances, one for each follower

    The twitter.Api instance must be authenticated.

    Returns:
      A sequence of twitter.User instances, one for each follower
    '''
    if not self._username:
      raise TwitterError("twitter.Api instance must be authenticated")
    url = 'http://twitter.com/statuses/followers.json'
    json = self._FetchUrl(url)
    data = simplejson.loads(json)
    self._CheckForTwitterError(data)
    return [User.NewFromJsonDict(x) for x in data]

  def GetFeatured(self):
    '''Fetch the sequence of twitter.User instances featured on twitter.com

    The twitter.Api instance must be authenticated.

    Returns:
      A sequence of twitter.User instances
    '''
    url = 'http://twitter.com/statuses/featured.json'
    json = self._FetchUrl(url)
    data = simplejson.loads(json)
    self._CheckForTwitterError(data)
    return [User.NewFromJsonDict(x) for x in data]

  def GetUser(self, user):
    '''Returns a single user.

    The twitter.Api instance must be authenticated.

    Args:
      user: The username or id of the user to retrieve.

    Returns:
      A twitter.User instance representing that user
    '''
    url = 'http://twitter.com/users/show/%s.json' % user
    json = self._FetchUrl(url)
    data = simplejson.loads(json)
    self._CheckForTwitterError(data)
    return User.NewFromJsonDict(data)

  def GetDirectMessages(self, since=None, since_id=None):
    '''Returns a list of the direct messages sent to the authenticating user.

    The twitter.Api instance must be authenticated.

    Args:
      since:
        Narrows the returned results to just those statuses created
        after the specified HTTP-formatted date. [optional]
      since_id:
        Returns only public statuses with an ID greater than (that is,
        more recent than) the specified ID. [Optional]

    Returns:
      A sequence of twitter.DirectMessage instances
    '''
    url = 'http://twitter.com/direct_messages.json'
    if not self._username:
      raise TwitterError("The twitter.Api instance must be authenticated.")
    parameters = {}
    if since:
      parameters['since'] = since
    if since_id:
      parameters['since_id'] = since_id
    json = self._FetchUrl(url, parameters=parameters)
    data = simplejson.loads(json)
    self._CheckForTwitterError(data)
    return [DirectMessage.NewFromJsonDict(x) for x in data]

  def PostDirectMessage(self, user, text):
    '''Post a twitter direct message from the authenticated user

    The twitter.Api instance must be authenticated.

    Args:
      user: The ID or screen name of the recipient user.
      text: The message text to be posted.  Must be less than 140 characters.

    Returns:
      A twitter.DirectMessage instance representing the message posted
    '''
    if not self._username:
      raise TwitterError("The twitter.Api instance must be authenticated.")
    url = 'http://twitter.com/direct_messages/new.json'
    data = {'text': text, 'user': user}
    json = self._FetchUrl(url, post_data=data)
    data = simplejson.loads(json)
    self._CheckForTwitterError(data)
    return DirectMessage.NewFromJsonDict(data)

  def DestroyDirectMessage(self, id):
    '''Destroys the direct message specified in the required ID parameter.

    The twitter.Api instance must be authenticated, and the
    authenticating user must be the recipient of the specified direct
    message.

    Args:
      id: The id of the direct message to be destroyed

    Returns:
      A twitter.DirectMessage instance representing the message destroyed
    '''
    url = 'http://twitter.com/direct_messages/destroy/%s.json' % id
    json = self._FetchUrl(url, post_data={})
    data = simplejson.loads(json)
    self._CheckForTwitterError(data)
    return DirectMessage.NewFromJsonDict(data)

  def CreateFriendship(self, user):
    '''Befriends the user specified in the user parameter as the authenticating user.

    The twitter.Api instance must be authenticated.

    Args:
      The ID or screen name of the user to befriend.
    Returns:
      A twitter.User instance representing the befriended user.
    '''
    url = 'http://twitter.com/friendships/create/%s.json' % user
    json = self._FetchUrl(url, post_data={})
    data = simplejson.loads(json)
    self._CheckForTwitterError(data)
    return User.NewFromJsonDict(data)

  def DestroyFriendship(self, user):
    '''Discontinues friendship with the user specified in the user parameter.

    The twitter.Api instance must be authenticated.

    Args:
      The ID or screen name of the user  with whom to discontinue friendship.
    Returns:
      A twitter.User instance representing the discontinued friend.
    '''
    url = 'http://twitter.com/friendships/destroy/%s.json' % user
    json = self._FetchUrl(url, post_data={})
    data = simplejson.loads(json)
    self._CheckForTwitterError(data)
    return User.NewFromJsonDict(data)

  def CreateFavorite(self, status):
    '''Favorites the status specified in the status parameter as the authenticating user.
    Returns the favorite status when successful.

    The twitter.Api instance must be authenticated.

    Args:
      The twitter.Status instance to mark as a favorite.
    Returns:
      A twitter.Status instance representing the newly-marked favorite.
    '''
    url = 'http://twitter.com/favorites/create/%s.json' % status.id
    json = self._FetchUrl(url, post_data={})
    data = simplejson.loads(json)
    self._CheckForTwitterError(data)
    return Status.NewFromJsonDict(data)

  def DestroyFavorite(self, status):
    '''Un-favorites the status specified in the ID parameter as the authenticating user.
    Returns the un-favorited status in the requested format when successful.

    The twitter.Api instance must be authenticated.

    Args:
      The twitter.Status to unmark as a favorite.
    Returns:
      A twitter.Status instance representing the newly-unmarked favorite.
    '''
    url = 'http://twitter.com/favorites/destroy/%s.json' % status.id
    json = self._FetchUrl(url, post_data={})
    data = simplejson.loads(json)
    self._CheckForTwitterError(data)
    return Status.NewFromJsonDict(data)

  def GetUserByEmail(self, email):
    '''Returns a single user by email address.

    Args:
      email: The email of the user to retrieve.
    Returns:
      A twitter.User instance representing that user
    '''
    url = 'http://twitter.com/users/show.json?email=%s' % email
    json = self._FetchUrl(url)
    data = simplejson.loads(json)
    self._CheckForTwitterError(data)
    return User.NewFromJsonDict(data)

  def SetCredentials(self, username, password):
    '''Set the username and password for this instance

    Args:
      username: The twitter username.
      password: The twitter password.
    '''
    self._username = username
    self._password = password

  def ClearCredentials(self):
    '''Clear the username and password for this instance
    '''
    self._username = None
    self._password = None

  def SetCache(self, cache):
    '''Override the default cache.  Set to None to prevent caching.

    Args:
      cache: an instance that supports the same API as the  twitter._FileCache
    '''
    self._cache = cache

  def SetUrllib(self, urllib):
    '''Override the default urllib implementation.

    Args:
      urllib: an instance that supports the same API as the urllib2 module
    '''
    self._urllib = urllib

  def SetCacheTimeout(self, cache_timeout):
    '''Override the default cache timeout.

    Args:
      cache_timeout: time, in seconds, that responses should be reused.
    '''
    self._cache_timeout = cache_timeout

  def SetUserAgent(self, user_agent):
    '''Override the default user agent

    Args:
      user_agent: a string that should be send to the server as the User-agent
    '''
    self._request_headers['User-Agent'] = user_agent

  def SetXTwitterHeaders(self, client, url, version):
    '''Set the X-Twitter HTTP headers that will be sent to the server.

    Args:
      client:
         The client name as a string.  Will be sent to the server as
         the 'X-Twitter-Client' header.
      url:
         The URL of the meta.xml as a string.  Will be sent to the server
         as the 'X-Twitter-Client-URL' header.
      version:
         The client version as a string.  Will be sent to the server
         as the 'X-Twitter-Client-Version' header.
    '''
    self._request_headers['X-Twitter-Client'] = client
    self._request_headers['X-Twitter-Client-URL'] = url
    self._request_headers['X-Twitter-Client-Version'] = version

  def SetSource(self, source):
    '''Suggest the "from source" value to be displayed on the Twitter web site.

    The value of the 'source' parameter must be first recognized by
    the Twitter server.  New source values are authorized on a case by
    case basis by the Twitter development team.

    Args:
      source:
        The source name as a string.  Will be sent to the server as
        the 'source' parameter.
    '''
    self._default_params['source'] = source

  def _BuildUrl(self, url, path_elements=None, extra_params=None):
    # Break url into consituent parts
    (scheme, netloc, path, params, query, fragment) = urlparse.urlparse(url)

    # Add any additional path elements to the path
    if path_elements:
      # Filter out the path elements that have a value of None
      p = [i for i in path_elements if i]
      if not path.endswith('/'):
        path += '/'
      path += '/'.join(p)

    # Add any additional query parameters to the query string
    if extra_params and len(extra_params) > 0:
      extra_query = self._EncodeParameters(extra_params)
      # Add it to the existing query
      if query:
        query += '&' + extra_query
      else:
        query = extra_query

    # Return the rebuilt URL
    return urlparse.urlunparse((scheme, netloc, path, params, query, fragment))

  def _InitializeRequestHeaders(self, request_headers):
    if request_headers:
      self._request_headers = request_headers
    else:
      self._request_headers = {}

  def _InitializeUserAgent(self):
    user_agent = 'Python-urllib/%s (python-twitter/%s)' % \
                 (self._urllib.__version__, __version__)
    self.SetUserAgent(user_agent)

  def _InitializeDefaultParameters(self):
    self._default_params = {}

  def _AddAuthorizationHeader(self, username, password):
    if username and password:
      basic_auth = base64.encodestring('%s:%s' % (username, password))[:-1]
      self._request_headers['Authorization'] = 'Basic %s' % basic_auth

  def _RemoveAuthorizationHeader(self):
    if self._request_headers and 'Authorization' in self._request_headers:
      del self._request_headers['Authorization']

  def _GetOpener(self, url, username=None, password=None):
    if username and password:
      self._AddAuthorizationHeader(username, password)
      handler = self._urllib.HTTPBasicAuthHandler()
      (scheme, netloc, path, params, query, fragment) = urlparse.urlparse(url)
      handler.add_password(Api._API_REALM, netloc, username, password)
      opener = self._urllib.build_opener(handler)
    else:
      opener = self._urllib.build_opener()
    opener.addheaders = self._request_headers.items()
    return opener

  def _Encode(self, s):
    if self._input_encoding:
      return unicode(s, self._input_encoding).encode('utf-8')
    else:
      return unicode(s).encode('utf-8')

  def _EncodeParameters(self, parameters):
    '''Return a string in key=value&key=value form

    Values of None are not included in the output string.

    Args:
      parameters:
        A dict of (key, value) tuples, where value is encoded as
        specified by self._encoding
    Returns:
      A URL-encoded string in "key=value&key=value" form
    '''
    if parameters is None:
      return None
    else:
      return urllib.urlencode(dict([(k, self._Encode(v)) for k, v in parameters.items() if v is not None]))

  def _EncodePostData(self, post_data):
    '''Return a string in key=value&key=value form

    Values are assumed to be encoded in the format specified by self._encoding,
    and are subsequently URL encoded.

    Args:
      post_data:
        A dict of (key, value) tuples, where value is encoded as
        specified by self._encoding
    Returns:
      A URL-encoded string in "key=value&key=value" form
    '''
    if post_data is None:
      return None
    else:
      return urllib.urlencode(dict([(k, self._Encode(v)) for k, v in post_data.items()]))

  def _CheckForTwitterError(self, data):
    """Raises a TwitterError if twitter returns an error message.

    Args:
      data: A python dict created from the Twitter json response
    Raises:
      TwitterError wrapping the twitter error message if one exists.
    """
    # Twitter errors are relatively unlikely, so it is faster
    # to check first, rather than try and catch the exception
    if 'error' in data:
      raise TwitterError(data['error'])

  def _FetchUrl(self,
                url,
                post_data=None,
                parameters=None,
                no_cache=None):
    '''Fetch a URL, optionally caching for a specified time.

    Args:
      url: The URL to retrieve
      post_data: 
        A dict of (str, unicode) key/value pairs.  If set, POST will be used.
      parameters:
        A dict whose key/value pairs should encoded and added 
        to the query string. [OPTIONAL]
      no_cache: If true, overrides the cache on the current request

    Returns:
      A string containing the body of the response.
    '''
    # Build the extra parameters dict
    extra_params = {}
    if self._default_params:
      extra_params.update(self._default_params)
    if parameters:
      extra_params.update(parameters)

    # Add key/value parameters to the query string of the url
    url = self._BuildUrl(url, extra_params=extra_params)

    # Get a url opener that can handle basic auth
    opener = self._GetOpener(url, username=self._username, password=self._password)

    encoded_post_data = self._EncodePostData(post_data)

    # Open and return the URL immediately if we're not going to cache
    if encoded_post_data or no_cache or not self._cache or not self._cache_timeout:
      url_data = opener.open(url, encoded_post_data).read()
    else:
      # Unique keys are a combination of the url and the username
      if self._username:
        key = self._username + ':' + url
      else:
        key = url

      # See if it has been cached before
      last_cached = self._cache.GetCachedTime(key)

      # If the cached version is outdated then fetch another and store it
      if not last_cached or time.time() >= last_cached + self._cache_timeout:
        url_data = opener.open(url, encoded_post_data).read()
        self._cache.Set(key, url_data)
      else:
        url_data = self._cache.Get(key)

    # Always return the latest version
    return url_data

class _FileCacheError(Exception):
  '''Base exception class for FileCache related errors'''

class _FileCache(object):

  DEPTH = 3

  def __init__(self,root_directory=None):
    self._InitializeRootDirectory(root_directory)

  def Get(self,key):
    path = self._GetPath(key)
    if os.path.exists(path):
      return open(path).read()
    else:
      return None

  def Set(self,key,data):
    path = self._GetPath(key)
    directory = os.path.dirname(path)
    if not os.path.exists(directory):
      os.makedirs(directory)
    if not os.path.isdir(directory):
      raise _FileCacheError('%s exists but is not a directory' % directory)
    temp_fd, temp_path = tempfile.mkstemp()
    temp_fp = os.fdopen(temp_fd, 'w')
    temp_fp.write(data)
    temp_fp.close()
    if not path.startswith(self._root_directory):
      raise _FileCacheError('%s does not appear to live under %s' %
                            (path, self._root_directory))
    if os.path.exists(path):
      os.remove(path)
    os.rename(temp_path, path)

  def Remove(self,key):
    path = self._GetPath(key)
    if not path.startswith(self._root_directory):
      raise _FileCacheError('%s does not appear to live under %s' %
                            (path, self._root_directory ))
    if os.path.exists(path):
      os.remove(path)

  def GetCachedTime(self,key):
    path = self._GetPath(key)
    if os.path.exists(path):
      return os.path.getmtime(path)
    else:
      return None

  def _GetUsername(self):
    '''Attempt to find the username in a cross-platform fashion.'''
    try:
      return os.getenv('USER') or \
             os.getenv('LOGNAME') or \
             os.getenv('USERNAME') or \
             os.getlogin() or \
             'nobody'
    except (IOError, OSError), e:
      return 'nobody'

  def _GetTmpCachePath(self):
    username = self._GetUsername()
    cache_directory = 'python.cache_' + username
    return os.path.join(tempfile.gettempdir(), cache_directory)

  def _InitializeRootDirectory(self, root_directory):
    if not root_directory:
      root_directory = self._GetTmpCachePath()
    root_directory = os.path.abspath(root_directory)
    if not os.path.exists(root_directory):
      os.mkdir(root_directory)
    if not os.path.isdir(root_directory):
      raise _FileCacheError('%s exists but is not a directory' %
                            root_directory)
    self._root_directory = root_directory

  def _GetPath(self,key):
    hashed_key = md5.new(key).hexdigest()
    return os.path.join(self._root_directory,
                        self._GetPrefix(hashed_key),
                        hashed_key)

  def _GetPrefix(self,hashed_key):
    return os.path.sep.join(hashed_key[0:_FileCache.DEPTH])