sam-t2/devtools/v8plus/html/python/lib/optparse-how-callbacks-called.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="optparse-raising-errors-in-callback.html" />
<link rel="prev" href="optparse-defining-callback-option.html" />
<link rel="parent" href="optparse-option-callbacks.html" />
<link rel="next" href="optparse-raising-errors-in-callback.html" />
<meta name='aesop' content='information' />
<title>6.21.4.2 How callbacks are called</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="6.21.4.1 Defining a callback"
  href="optparse-defining-callback-option.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="6.21.4 Option Callbacks"
  href="optparse-option-callbacks.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="6.21.4.3 Raising errors in"
  href="optparse-raising-errors-in-callback.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="optparse-defining-callback-option.html">6.21.4.1 Defining a callback</A>
<b class="navlabel">Up:</b>
<a class="sectref" rel="parent" href="optparse-option-callbacks.html">6.21.4 Option Callbacks</A>
<b class="navlabel">Next:</b>
<a class="sectref" rel="next" href="optparse-raising-errors-in-callback.html">6.21.4.3 Raising errors in</A>
</div>
<hr /></div>
</DIV>
<!--End of Navigation Panel-->

<H3><A NAME="SECTION0082142000000000000000"></A><A NAME="optparse-how-callbacks-called"></A>
<BR>
6.21.4.2 How callbacks are called
</H3>

<P>
All callbacks are called as follows:
<div class="verbatim"><pre>
func(option, opt_str, value, parser, *args, **kwargs)
</pre></div>

<P>
where
<DL>
<DT><STRONG><code>option</code></STRONG></DT>
<DD>is the Option instance that's calling the callback
</DD>
<DT><STRONG><code>opt_str</code></STRONG></DT>
<DD>is the option string seen on the command-line that's triggering the
callback.  (If an abbreviated long option was used, <code>opt_str</code> will
be the full, canonical option string--e.g. if the user puts
<code>"-foo"</code> on the command-line as an abbreviation for
<code>"-foobar"</code>, then <code>opt_str</code> will be <code>"-foobar"</code>.)
</DD>
<DT><STRONG><code>value</code></STRONG></DT>
<DD>is the argument to this option seen on the command-line.  <tt class="module">optparse</tt> will
only expect an argument if <tt class="member">type</tt> is set; the type of <code>value</code>
will be the type implied by the option's type.  If <tt class="member">type</tt> for this
option is <code>None</code> (no argument expected), then <code>value</code> will be
<code>None</code>.  If <code>nargs</code> &gt; 1, <code>value</code> will be a tuple of values of
the appropriate type.
</DD>
<DT><STRONG><code>parser</code></STRONG></DT>
<DD>is the OptionParser instance driving the whole thing, mainly
useful because you can access some other interesting data through
its instance attributes:
<DL>
<DT><STRONG><code>parser.largs</code></STRONG></DT>
<DD>the current list of leftover arguments, ie. arguments that have
been consumed but are neither options nor option arguments.
Feel free to modify <code>parser.largs</code>, e.g. by adding more
arguments to it.  (This list will become <code>args</code>, the second
return value of <tt class="method">parse_args()</tt>.)
</DD>
<DT><STRONG><code>parser.rargs</code></STRONG></DT>
<DD>the current list of remaining arguments, ie. with <code>opt_str</code> and
<code>value</code> (if applicable) removed, and only the arguments
following them still there.  Feel free to modify
<code>parser.rargs</code>, e.g. by consuming more arguments.
</DD>
<DT><STRONG><code>parser.values</code></STRONG></DT>
<DD>the object where option values are by default stored (an
instance of optparse.OptionValues).  This lets callbacks use the
same mechanism as the rest of <tt class="module">optparse</tt> for storing option values;
you don't need to mess around with globals or closures.  You can
also access or modify the value(s) of any options already
encountered on the command-line.
</DD>
</DL>
</DD>
<DT><STRONG><code>args</code></STRONG></DT>
<DD>is a tuple of arbitrary positional arguments supplied via the
<code>callback_args</code> option attribute.
</DD>
<DT><STRONG><code>kwargs</code></STRONG></DT>
<DD>is a dictionary of arbitrary keyword arguments supplied via
<code>callback_kwargs</code>.
</DD>
</DL>

<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="6.21.4.1 Defining a callback"
  href="optparse-defining-callback-option.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="6.21.4 Option Callbacks"
  href="optparse-option-callbacks.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="6.21.4.3 Raising errors in"
  href="optparse-raising-errors-in-callback.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="optparse-defining-callback-option.html">6.21.4.1 Defining a callback</A>
<b class="navlabel">Up:</b>
<a class="sectref" rel="parent" href="optparse-option-callbacks.html">6.21.4 Option Callbacks</A>
<b class="navlabel">Next:</b>
<a class="sectref" rel="next" href="optparse-raising-errors-in-callback.html">6.21.4.3 Raising errors in</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>