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<title>6.21.3.7 Parsing arguments
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<H3><A NAME=
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"optparse-parsing-arguments"></A>
6.21.3.7 Parsing arguments
The whole point of creating and populating an OptionParser is to call
its
<tt class=
"method">parse_args()
</tt> method:
<div class=
"verbatim"><pre>
(options, args) = parser.parse_args(args=None, options=None)
where the input parameters are
<DT><STRONG><code>args
</code></STRONG></DT>
<DD>the list of arguments to process (
<code>sys.argv[
1:]
</code> by default)
<DT><STRONG><code>options
</code></STRONG></DT>
<DD>object to store option arguments in (a new instance of
optparse.Values by default)
and the return values are
<DT><STRONG><code>options
</code></STRONG></DT>
<DD>the same object as was passed in as
<code>options
</code>, or the new
optparse.Values instance created by
<tt class=
"module">optparse
</tt>
<DT><STRONG><code>args
</code></STRONG></DT>
<DD>the leftover positional arguments after all options have been
The most common usage is to supply neither keyword argument. If you
supply a
<code>values
</code> object, it will be repeatedly modified with a
<code>setattr()
</code> call for every option argument written to an option
destination, and finally returned by
<tt class=
"method">parse_args()
</tt>.
If
<tt class=
"method">parse_args()
</tt> encounters any errors in the argument list, it calls
the OptionParser's
<tt class=
"method">error()
</tt> method with an appropriate end-user error
message. This ultimately terminates your process with an exit status of
2 (the traditional
<span class=
"Unix">Unix
</span> exit status for command-line errors).
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<span class=
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2005.
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