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| 55 | <H3><A NAME="SECTION0082137000000000000000"></A><A NAME="optparse-parsing-arguments"></A> |
| 56 | <BR> |
| 57 | 6.21.3.7 Parsing arguments |
| 58 | </H3> |
| 59 | |
| 60 | <P> |
| 61 | The whole point of creating and populating an OptionParser is to call |
| 62 | its <tt class="method">parse_args()</tt> method: |
| 63 | <div class="verbatim"><pre> |
| 64 | (options, args) = parser.parse_args(args=None, options=None) |
| 65 | </pre></div> |
| 66 | |
| 67 | <P> |
| 68 | where the input parameters are |
| 69 | <DL> |
| 70 | <DT><STRONG><code>args</code></STRONG></DT> |
| 71 | <DD>the list of arguments to process (<code>sys.argv[1:]</code> by default) |
| 72 | </DD> |
| 73 | <DT><STRONG><code>options</code></STRONG></DT> |
| 74 | <DD>object to store option arguments in (a new instance of |
| 75 | optparse.Values by default) |
| 76 | </DD> |
| 77 | </DL> |
| 78 | |
| 79 | <P> |
| 80 | and the return values are |
| 81 | <DL> |
| 82 | <DT><STRONG><code>options</code></STRONG></DT> |
| 83 | <DD>the same object as was passed in as <code>options</code>, or the new |
| 84 | optparse.Values instance created by <tt class="module">optparse</tt> |
| 85 | </DD> |
| 86 | <DT><STRONG><code>args</code></STRONG></DT> |
| 87 | <DD>the leftover positional arguments after all options have been |
| 88 | processed |
| 89 | </DD> |
| 90 | </DL> |
| 91 | |
| 92 | <P> |
| 93 | The most common usage is to supply neither keyword argument. If you |
| 94 | supply a <code>values</code> object, it will be repeatedly modified with a |
| 95 | <code>setattr()</code> call for every option argument written to an option |
| 96 | destination, and finally returned by <tt class="method">parse_args()</tt>. |
| 97 | |
| 98 | <P> |
| 99 | If <tt class="method">parse_args()</tt> encounters any errors in the argument list, it calls |
| 100 | the OptionParser's <tt class="method">error()</tt> method with an appropriate end-user error |
| 101 | message. This ultimately terminates your process with an exit status of |
| 102 | 2 (the traditional <span class="Unix">Unix</span> exit status for command-line errors). |
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