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<H3><A NAME="SECTION0082122000000000000000"></A><A NAME="optparse-store-action"></A>
<BR>
6.21.2.2 The store action
</H3>

<P>
The most common option action is <code>store</code>, which tells <tt class="module">optparse</tt> to take
the next argument (or the remainder of the current argument), ensure
that it is of the correct type, and store it to your chosen destination.

<P>
For example:
<div class="verbatim"><pre>
parser.add_option("-f", "--file",
                  action="store", type="string", dest="filename")
</pre></div>

<P>
Now let's make up a fake command line and ask <tt class="module">optparse</tt> to parse it:
<div class="verbatim"><pre>
args = ["-f", "foo.txt"]
(options, args) = parser.parse_args(args)
</pre></div>

<P>
When <tt class="module">optparse</tt> sees the option string <code>"-f"</code>, it consumes the next
argument, <code>"foo.txt"</code>, and stores it in <code>options.filename</code>.  So,
after this call to <tt class="method">parse_args()</tt>, <code>options.filename</code> is
<code>"foo.txt"</code>.

<P>
Some other option types supported by <tt class="module">optparse</tt> are <code>int</code> and <code>float</code>.
Here's an option that expects an integer argument:
<div class="verbatim"><pre>
parser.add_option("-n", type="int", dest="num")
</pre></div>

<P>
Note that this option has no long option string, which is perfectly
acceptable.  Also, there's no explicit action, since the default is
<code>store</code>.

<P>
Let's parse another fake command-line.  This time, we'll jam the option
argument right up against the option: since <code>"-n42"</code> (one argument) is
equivalent to <code>"-n 42"</code> (two arguments), the code
<div class="verbatim"><pre>
(options, args) = parser.parse_args(["-n42"])
print options.num
</pre></div>

<P>
will print <code>"42"</code>.

<P>
If you don't specify a type, <tt class="module">optparse</tt> assumes <code>string</code>.  Combined with the
fact that the default action is <code>store</code>, that means our first example
can be a lot shorter:
<div class="verbatim"><pre>
parser.add_option("-f", "--file", dest="filename")
</pre></div>

<P>
If you don't supply a destination, <tt class="module">optparse</tt> figures out a sensible default
from the option strings: if the first long option string is
<code>"-foo-bar"</code>, then the default destination is <code>foo_bar</code>.  If there
are no long option strings, <tt class="module">optparse</tt> looks at the first short option
string: the default destination for <code>"-f"</code> is <code>f</code>.

<P>
<tt class="module">optparse</tt> also includes built-in <code>long</code> and <code>complex</code> types.  Adding
types is covered in section&nbsp;<A HREF="#optparse-extending"><tex2html_cross_ref_visible_mark></A>, Extending <tt class="module">optparse</tt>.

<P>

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<span class="release-info">Release 2.4.2, documentation updated on 28 September 2005.</span>
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