OpenerDirector instances have the following methods:
add_handler(
handler)
handler should be an instance of BaseHandler. The
following methods are searched, and added to the possible chains (note
that HTTP errors are a special case).
protocol_open() --
signal that the handler knows how to open protocol URLs.
http_error_type() --
signal that the handler knows how to handle HTTP errors with HTTP
error code type.
protocol_error() --
signal that the handler knows how to handle errors from
(non-http) protocol.
protocol_request() --
signal that the handler knows how to pre-process protocol
requests.
protocol_response() --
signal that the handler knows how to post-process protocol
responses.
open(
url[, data])
Open the given url (which can be a request object or a string),
optionally passing the given data.
Arguments, return values and exceptions raised are the same as those
of urlopen() (which simply calls the open() method
on the currently installed global OpenerDirector).
error(
proto[,
arg[, ...]])
Handle an error of the given protocol. This will call the registered
error handlers for the given protocol with the given arguments (which
are protocol specific). The HTTP protocol is a special case which
uses the HTTP response code to determine the specific error handler;
refer to the http_error_*() methods of the handler classes.
Return values and exceptions raised are the same as those
of urlopen().
OpenerDirector objects open URLs in three stages:
The order in which these methods are called within each stage is
determined by sorting the handler instances.
Every handler with a method named like
protocol_request() has that method called to
pre-process the request.
Handlers with a method named like
protocol_open() are called to handle the request.
This stage ends when a handler either returns a
non-None value (ie. a response), or raises an exception
(usually URLError). Exceptions are allowed to propagate.
In fact, the above algorithm is first tried for methods named
default_open. If all such methods return
None, the algorithm is repeated for methods named like
protocol_open(). If all such methods return
None, the algorithm is repeated for methods named
unknown_open().
Note that the implementation of these methods may involve calls of
the parent OpenerDirector instance's .open() and
.error() methods.
Every handler with a method named like
protocol_response() has that method called to
post-process the response.
