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<title>6.21 optparse -- More powerful command line option parser</title>
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<H1><A NAME="SECTION0082100000000000000000">
6.21 <tt class="module">optparse</tt> -- More powerful command line option parser</A>
</H1>
<A NAME="module-optparse"></A>

<span class="versionnote">New in version 2.3.</span>

<P>
<code>optparse</code> is a more convenient, flexible, and powerful library for
parsing command-line options than <code>getopt</code>.  <code>optparse</code> uses a more
declarative style of command-line parsing: you create an instance of
<tt class="class">OptionParser</tt>, populate it with options, and parse the command line.
<code>optparse</code> allows users to specify options in the conventional GNU/POSIX
syntax, and additionally generates usage and help messages for you.

<P>
Here's an example of using <code>optparse</code> in a simple script:
<div class="verbatim"><pre>
from optparse import OptionParser
[...]
parser = OptionParser()
parser.add_option("-f", "--file", dest="filename",
                  help="write report to FILE", metavar="FILE")
parser.add_option("-q", "--quiet",
                  action="store_false", dest="verbose", default=True,
                  help="don't print status messages to stdout")

(options, args) = parser.parse_args()
</pre></div>

<P>
With these few lines of code, users of your script can now do the
``usual thing'' on the command-line, for example:
<div class="verbatim"><pre>
&lt;yourscript&gt; --file=outfile -q
</pre></div>

<P>
As it parses the command line, <code>optparse</code> sets attributes of the
<code>options</code> object returned by <tt class="method">parse_args()</tt> based on user-supplied
command-line values.  When <tt class="method">parse_args()</tt> returns from parsing this
command line, <code>options.filename</code> will be <code>"outfile"</code> and
<code>options.verbose</code> will be <code>False</code>.  <code>optparse</code> supports both long
and short options, allows short options to be merged together, and
allows options to be associated with their arguments in a variety of
ways.  Thus, the following command lines are all equivalent to the above
example:
<div class="verbatim"><pre>
&lt;yourscript&gt; -f outfile --quiet
&lt;yourscript&gt; --quiet --file outfile
&lt;yourscript&gt; -q -foutfile
&lt;yourscript&gt; -qfoutfile
</pre></div>

<P>
Additionally, users can run one of
<div class="verbatim"><pre>
&lt;yourscript&gt; -h
&lt;yourscript&gt; --help
</pre></div>

<P>
and <code>optparse</code> will print out a brief summary of your script's
options:
<div class="verbatim"><pre>
usage: &lt;yourscript&gt; [options]

options:
  -h, --help            show this help message and exit
  -f FILE, --file=FILE  write report to FILE
  -q, --quiet           don't print status messages to stdout
</pre></div>

<P>
where the value of <em>yourscript</em> is determined at runtime (normally
from <code>sys.argv[0]</code>).

<P>

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<A NAME="CHILD_LINKS"><STRONG>Subsections</STRONG></a>

<UL CLASS="ChildLinks">
<LI><A href="optparse-background.html">6.21.1 Background</a>
<UL>
<LI><A href="optparse-terminology.html">6.21.1.1 Terminology</a>
<LI><A href="optparse-what-options-for.html">6.21.1.2 What are options for?</a>
<LI><A href="optparse-what-positional-arguments-for.html">6.21.1.3 What are positional arguments for?</a>
</ul>
<LI><A href="optparse-tutorial.html">6.21.2 Tutorial</a>
<UL>
<LI><A href="optparse-understanding-option-actions.html">6.21.2.1 Understanding option actions</a>
<LI><A href="optparse-store-action.html">6.21.2.2 The store action</a>
<LI><A href="optparse-handling-boolean-options.html">6.21.2.3 Handling boolean (flag) options</a>
<LI><A href="optparse-other-actions.html">6.21.2.4 Other actions</a>
<LI><A href="optparse-default-values.html">6.21.2.5 Default values</a>
<LI><A href="optparse-generating-help.html">6.21.2.6 Generating help</a>
<LI><A href="optparse-printing-version-string.html">6.21.2.7 Printing a version string</a>
<LI><A href="optparse-how-optparse-handles-errors.html">6.21.2.8 How <tt class="module">optparse</tt> handles errors</a>
<LI><A href="optparse-putting-it-all-together.html">6.21.2.9 Putting it all together</a>
</ul>
<LI><A href="optparse-reference-guide.html">6.21.3 Reference Guide</a>
<UL>
<LI><A href="optparse-creating-parser.html">6.21.3.1 Creating the parser</a>
<LI><A href="optparse-populating-parser.html">6.21.3.2 Populating the parser</a>
<LI><A href="optparse-defining-options.html">6.21.3.3 Defining options</a>
<LI><A href="optparse-standard-option-actions.html">6.21.3.4 Standard option actions</a>
<LI><A href="optparse-option-attributes.html">6.21.3.5 Option attributes</a>
<LI><A href="optparse-standard-option-types.html">6.21.3.6 Standard option types</a>
<LI><A href="optparse-parsing-arguments.html">6.21.3.7 Parsing arguments</a>
<LI><A href="optparse-querying-manipulating-option-parser.html">6.21.3.8 Querying and manipulating your option parser</a>
<LI><A href="optparse-conflicts-between-options.html">6.21.3.9 Conflicts between options</a>
<LI><A href="optparse-other-methods.html">6.21.3.10 Other methods</a>
</ul>
<LI><A href="optparse-option-callbacks.html">6.21.4 Option Callbacks</a>
<UL>
<LI><A href="optparse-defining-callback-option.html">6.21.4.1 Defining a callback option</a>
<LI><A href="optparse-how-callbacks-called.html">6.21.4.2 How callbacks are called</a>
<LI><A href="optparse-raising-errors-in-callback.html">6.21.4.3 Raising errors in a callback</a>
<LI><A href="optparse-callback-example-1.html">6.21.4.4 Callback example 1: trivial callback</a>
<LI><A href="optparse-callback-example-2.html">6.21.4.5 Callback example 2: check option order</a>
<LI><A href="optparse-callback-example-3.html">6.21.4.6 Callback example 3: check option order (generalized)</a>
<LI><A href="optparse-callback-example-4.html">6.21.4.7 Callback example 4: check arbitrary condition</a>
<LI><A href="optparse-callback-example-5.html">6.21.4.8 Callback example 5: fixed arguments</a>
<LI><A href="optparse-callback-example-6.html">6.21.4.9 Callback example 6: variable arguments</a>
</ul>
<LI><A href="optparse-extending-optparse.html">6.21.5 Extending <tt class="module">optparse</tt></a>
<UL>
<LI><A href="optparse-adding-new-types.html">6.21.5.1 Adding new types</a>
<LI><A href="optparse-adding-new-actions.html">6.21.5.2 Adding new actions</a>
<LI><A href="optparse-other-reasons-to-extend-optparse.html">6.21.5.3 Other reasons to extend <tt class="module">optparse</tt></a>
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<span class="release-info">Release 2.4.2, documentation updated on 28 September 2005.</span>
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