Module defaultargs

[('ip',
  '',
  'ip to report to the tracker (has no effect unless you are on the sa
me local network as the tracker)'),
 ('forwarded_port',
  0,
  'world-visible port number if it\'s different from the one the clien
t listens on locally'),
...

[('download_slice_size',
  16384,
  'how many bytes to query for per request.'),
 ('max_message_length',
  8388608,
  'maximum length prefix encoding you\'ll accept over the wire - large
r values get the connection dropped.'),
 ('socket_timeout', 300.0, 'seconds to wait between closing sockets wh
...