<!DOCTYPE html PUBLIC
"-//W3C//DTD HTML 4.0 Transitional//EN">
<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-callback-example-6.html" />
<link rel=
"prev" href=
"optparse-callback-example-4.html" />
<link rel=
"parent" href=
"optparse-option-callbacks.html" />
<link rel=
"next" href=
"optparse-callback-example-6.html" />
<meta name='aesop' content='information'
/>
<title>6.21.4.8 Callback example
5: fixed arguments
</title>
<div id='top-navigation-panel' xml:id='top-navigation-panel'
>
<table align=
"center" width=
"100%" cellpadding=
"0" cellspacing=
"2">
<td class='online-navigation'
><a rel=
"prev" title=
"6.21.4.7 Callback example 4:"
href=
"optparse-callback-example-4.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=
"6.21.4.9 Callback example 6:"
href=
"optparse-callback-example-6.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>
<div class='online-navigation'
>
<b class=
"navlabel">Previous:
</b>
<a class=
"sectref" rel=
"prev" href=
"optparse-callback-example-4.html">6.21.4.7 Callback example
4:
</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-callback-example-6.html">6.21.4.9 Callback example
6:
</A>
<!--End of Navigation Panel-->
<H3><A NAME=
"SECTION0082148000000000000000"></A><A NAME=
"optparse-callback-example-5"></A>
6.21.4.8 Callback example
5: fixed arguments
Things get slightly more interesting when you define callback options
that take a fixed number of arguments. Specifying that a callback
option takes arguments is similar to defining a
<code>store
</code> or
<code>append
</code>
option: if you define
<tt class=
"member">type
</tt>, then the option takes one argument that
must be convertible to that type; if you further define
<code>nargs
</code>, then
the option takes
<code>nargs
</code> arguments.
Here's an example that just emulates the standard
<code>store
</code> action:
<div class=
"verbatim"><pre>
def store_value(option, opt_str, value, parser):
setattr(parser.values, option.dest, value)
parser.add_option(
"--foo",
action=
"callback", callback=store_value,
type=
"int", nargs=
3,
dest=
"foo")
Note that
<tt class=
"module">optparse
</tt> takes care of consuming
3 arguments and converting them
to integers for you; all you have to do is store them. (Or whatever;
obviously you don't need a callback for this example.)
<div class='online-navigation'
>
<table align=
"center" width=
"100%" cellpadding=
"0" cellspacing=
"2">
<td class='online-navigation'
><a rel=
"prev" title=
"6.21.4.7 Callback example 4:"
href=
"optparse-callback-example-4.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=
"6.21.4.9 Callback example 6:"
href=
"optparse-callback-example-6.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>
<div class='online-navigation'
>
<b class=
"navlabel">Previous:
</b>
<a class=
"sectref" rel=
"prev" href=
"optparse-callback-example-4.html">6.21.4.7 Callback example
4:
</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-callback-example-6.html">6.21.4.9 Callback example
6:
</A>
<span class=
"release-info">Release
2.4.2, documentation updated on
28 September
2005.
</span>
<!--End of Navigation Panel-->
See
<i><a href=
"about.html">About this document...
</a></i> for information on suggesting changes.