sam-t2/devtools/v8plus/html/python/lib/opener-director-objects.html

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<html>
<head>
<link rel="STYLESHEET" href="lib.css" type='text/css' />
<link rel="SHORTCUT ICON" href="../icons/pyfav.png" type="image/png" />
<link rel='start' href='../index.html' title='Python Documentation Index' />
<link rel="first" href="lib.html" title='Python Library Reference' />
<link rel='contents' href='contents.html' title="Contents" />
<link rel='index' href='genindex.html' title='Index' />
<link rel='last' href='about.html' title='About this document...' />
<link rel='help' href='about.html' title='About this document...' />
<link rel="next" href="base-handler-objects.html" />
<link rel="prev" href="request-objects.html" />
<link rel="parent" href="module-urllib2.html" />
<link rel="next" href="base-handler-objects.html" />
<meta name='aesop' content='information' />
<title>11.5.2 OpenerDirector Objects </title>
</head>
<body>
<DIV CLASS="navigation">
<div id='top-navigation-panel' xml:id='top-navigation-panel'>
<table align="center" width="100%" cellpadding="0" cellspacing="2">
<tr>
<td class='online-navigation'><a rel="prev" title="11.5.1 Request Objects"
  href="request-objects.html"><img src='../icons/previous.png'
  border='0' height='32'  alt='Previous Page' width='32' /></A></td>
<td class='online-navigation'><a rel="parent" title="11.5 urllib2  "
  href="module-urllib2.html"><img src='../icons/up.png'
  border='0' height='32'  alt='Up One Level' width='32' /></A></td>
<td class='online-navigation'><a rel="next" title="11.5.3 BaseHandler Objects"
  href="base-handler-objects.html"><img src='../icons/next.png'
  border='0' height='32'  alt='Next Page' width='32' /></A></td>
<td align="center" width="100%">Python Library Reference</td>
<td class='online-navigation'><a rel="contents" title="Table of Contents"
  href="contents.html"><img src='../icons/contents.png'
  border='0' height='32'  alt='Contents' width='32' /></A></td>
<td class='online-navigation'><a href="modindex.html" title="Module Index"><img src='../icons/modules.png'
  border='0' height='32'  alt='Module Index' width='32' /></a></td>
<td class='online-navigation'><a rel="index" title="Index"
  href="genindex.html"><img src='../icons/index.png'
  border='0' height='32'  alt='Index' width='32' /></A></td>
</tr></table>
<div class='online-navigation'>
<b class="navlabel">Previous:</b>
<a class="sectref" rel="prev" href="request-objects.html">11.5.1 Request Objects</A>
<b class="navlabel">Up:</b>
<a class="sectref" rel="parent" href="module-urllib2.html">11.5 urllib2  </A>
<b class="navlabel">Next:</b>
<a class="sectref" rel="next" href="base-handler-objects.html">11.5.3 BaseHandler Objects</A>
</div>
<hr /></div>
</DIV>
<!--End of Navigation Panel-->

<H2><A NAME="SECTION0013520000000000000000"></A><A NAME="opener-director-objects"></A>
<BR>
11.5.2 OpenerDirector Objects
</H2>

<P>
<tt class="class">OpenerDirector</tt> instances have the following methods:

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-3261' xml:id='l2h-3261' class="method">add_handler</tt></b>(</nobr></td>
  <td><var>handler</var>)</td></tr></table></dt>
<dd>
<var>handler</var> should be an instance of <tt class="class">BaseHandler</tt>.  The
following methods are searched, and added to the possible chains (note
that HTTP errors are a special case).

<P>

<UL>
<LI><tt class="method"><var>protocol</var>_open()</tt> --
    signal that the handler knows how to open <var>protocol</var> URLs.
</LI>
<LI><tt class="method">http_error_<var>type</var>()</tt> --
    signal that the handler knows how to handle HTTP errors with HTTP
    error code <var>type</var>.
</LI>
<LI><tt class="method"><var>protocol</var>_error()</tt> --
    signal that the handler knows how to handle errors from
    (non-<code>http</code>) <var>protocol</var>.
</LI>
<LI><tt class="method"><var>protocol</var>_request()</tt> --
    signal that the handler knows how to pre-process <var>protocol</var>
    requests.
</LI>
<LI><tt class="method"><var>protocol</var>_response()</tt> --
    signal that the handler knows how to post-process <var>protocol</var>
    responses.
</LI>
</UL>
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-3262' xml:id='l2h-3262' class="method">open</tt></b>(</nobr></td>
  <td><var>url</var><big>[</big><var>, data</var><big>]</big><var></var>)</td></tr></table></dt>
<dd>
Open the given <var>url</var> (which can be a request object or a string),
optionally passing the given <var>data</var>.
Arguments, return values and exceptions raised are the same as those
of <tt class="function">urlopen()</tt> (which simply calls the <tt class="method">open()</tt> method
on the currently installed global <tt class="class">OpenerDirector</tt>).
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-3263' xml:id='l2h-3263' class="method">error</tt></b>(</nobr></td>
  <td><var>proto</var><big>[</big><var>,
                                          arg</var><big>[</big><var>, ...</var><big>]</big><var></var><big>]</big><var></var>)</td></tr></table></dt>
<dd>
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 <tt class="method">http_error_*()</tt> methods of the handler classes.

<P>
Return values and exceptions raised are the same as those
of <tt class="function">urlopen()</tt>.
</dl>

<P>
OpenerDirector objects open URLs in three stages:

<P>
The order in which these methods are called within each stage is
determined by sorting the handler instances.

<P>

<OL>
<LI>Every handler with a method named like
    <tt class="method"><var>protocol</var>_request()</tt> has that method called to
    pre-process the request.

<P>
</LI>
<LI>Handlers with a method named like
    <tt class="method"><var>protocol</var>_open()</tt> are called to handle the request.
    This stage ends when a handler either returns a
    non-<tt class="constant">None</tt> value (ie. a response), or raises an exception
    (usually URLError).  Exceptions are allowed to propagate.

<P>
In fact, the above algorithm is first tried for methods named
    <tt class="method">default_open</tt>.  If all such methods return
    <tt class="constant">None</tt>, the algorithm is repeated for methods named like
    <tt class="method"><var>protocol</var>_open()</tt>.  If all such methods return
    <tt class="constant">None</tt>, the algorithm is repeated for methods named
    <tt class="method">unknown_open()</tt>.

<P>
Note that the implementation of these methods may involve calls of
    the parent <tt class="class">OpenerDirector</tt> instance's <tt class="method">.open()</tt> and
    <tt class="method">.error()</tt> methods.

<P>
</LI>
<LI>Every handler with a method named like
    <tt class="method"><var>protocol</var>_response()</tt> has that method called to
    post-process the response.

<P>
</LI>
</OL>

<P>

<DIV CLASS="navigation">
<div class='online-navigation'>
<p></p><hr />
<table align="center" width="100%" cellpadding="0" cellspacing="2">
<tr>
<td class='online-navigation'><a rel="prev" title="11.5.1 Request Objects"
  href="request-objects.html"><img src='../icons/previous.png'
  border='0' height='32'  alt='Previous Page' width='32' /></A></td>
<td class='online-navigation'><a rel="parent" title="11.5 urllib2  "
  href="module-urllib2.html"><img src='../icons/up.png'
  border='0' height='32'  alt='Up One Level' width='32' /></A></td>
<td class='online-navigation'><a rel="next" title="11.5.3 BaseHandler Objects"
  href="base-handler-objects.html"><img src='../icons/next.png'
  border='0' height='32'  alt='Next Page' width='32' /></A></td>
<td align="center" width="100%">Python Library Reference</td>
<td class='online-navigation'><a rel="contents" title="Table of Contents"
  href="contents.html"><img src='../icons/contents.png'
  border='0' height='32'  alt='Contents' width='32' /></A></td>
<td class='online-navigation'><a href="modindex.html" title="Module Index"><img src='../icons/modules.png'
  border='0' height='32'  alt='Module Index' width='32' /></a></td>
<td class='online-navigation'><a rel="index" title="Index"
  href="genindex.html"><img src='../icons/index.png'
  border='0' height='32'  alt='Index' width='32' /></A></td>
</tr></table>
<div class='online-navigation'>
<b class="navlabel">Previous:</b>
<a class="sectref" rel="prev" href="request-objects.html">11.5.1 Request Objects</A>
<b class="navlabel">Up:</b>
<a class="sectref" rel="parent" href="module-urllib2.html">11.5 urllib2  </A>
<b class="navlabel">Next:</b>
<a class="sectref" rel="next" href="base-handler-objects.html">11.5.3 BaseHandler Objects</A>
</div>
</div>
<hr />
<span class="release-info">Release 2.4.2, documentation updated on 28 September 2005.</span>
</DIV>
<!--End of Navigation Panel-->
<ADDRESS>
See <i><a href="about.html">About this document...</a></i> for information on suggesting changes.
</ADDRESS>
</BODY>
</HTML>