Commit | Line | Data |
---|---|---|
920dae64 AT |
1 | <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> |
2 | <html> | |
3 | <head> | |
4 | <link rel="STYLESHEET" href="lib.css" type='text/css' /> | |
5 | <link rel="SHORTCUT ICON" href="../icons/pyfav.png" type="image/png" /> | |
6 | <link rel='start' href='../index.html' title='Python Documentation Index' /> | |
7 | <link rel="first" href="lib.html" title='Python Library Reference' /> | |
8 | <link rel='contents' href='contents.html' title="Contents" /> | |
9 | <link rel='index' href='genindex.html' title='Index' /> | |
10 | <link rel='last' href='about.html' title='About this document...' /> | |
11 | <link rel='help' href='about.html' title='About this document...' /> | |
12 | <link rel="prev" href="optparse-adding-new-actions.html" /> | |
13 | <link rel="parent" href="optparse-extending-optparse.html" /> | |
14 | <link rel="next" href="module-tempfile.html" /> | |
15 | <meta name='aesop' content='information' /> | |
16 | <title>6.21.5.3 Other reasons to extend optparse</title> | |
17 | </head> | |
18 | <body> | |
19 | <DIV CLASS="navigation"> | |
20 | <div id='top-navigation-panel' xml:id='top-navigation-panel'> | |
21 | <table align="center" width="100%" cellpadding="0" cellspacing="2"> | |
22 | <tr> | |
23 | <td class='online-navigation'><a rel="prev" title="6.21.5.2 Adding new actions" | |
24 | href="optparse-adding-new-actions.html"><img src='../icons/previous.png' | |
25 | border='0' height='32' alt='Previous Page' width='32' /></A></td> | |
26 | <td class='online-navigation'><a rel="parent" title="6.21.5 Extending optparse" | |
27 | href="optparse-extending-optparse.html"><img src='../icons/up.png' | |
28 | border='0' height='32' alt='Up One Level' width='32' /></A></td> | |
29 | <td class='online-navigation'><a rel="next" title="6.22 tempfile " | |
30 | href="module-tempfile.html"><img src='../icons/next.png' | |
31 | border='0' height='32' alt='Next Page' width='32' /></A></td> | |
32 | <td align="center" width="100%">Python Library Reference</td> | |
33 | <td class='online-navigation'><a rel="contents" title="Table of Contents" | |
34 | href="contents.html"><img src='../icons/contents.png' | |
35 | border='0' height='32' alt='Contents' width='32' /></A></td> | |
36 | <td class='online-navigation'><a href="modindex.html" title="Module Index"><img src='../icons/modules.png' | |
37 | border='0' height='32' alt='Module Index' width='32' /></a></td> | |
38 | <td class='online-navigation'><a rel="index" title="Index" | |
39 | href="genindex.html"><img src='../icons/index.png' | |
40 | border='0' height='32' alt='Index' width='32' /></A></td> | |
41 | </tr></table> | |
42 | <div class='online-navigation'> | |
43 | <b class="navlabel">Previous:</b> | |
44 | <a class="sectref" rel="prev" href="optparse-adding-new-actions.html">6.21.5.2 Adding new actions</A> | |
45 | <b class="navlabel">Up:</b> | |
46 | <a class="sectref" rel="parent" href="optparse-extending-optparse.html">6.21.5 Extending optparse</A> | |
47 | <b class="navlabel">Next:</b> | |
48 | <a class="sectref" rel="next" href="module-tempfile.html">6.22 tempfile </A> | |
49 | </div> | |
50 | <hr /></div> | |
51 | </DIV> | |
52 | <!--End of Navigation Panel--> | |
53 | ||
54 | <H3><A NAME="SECTION0082153000000000000000"></A><A NAME="optparse-other-reasons-to-extend-optparse"></A> | |
55 | <BR> | |
56 | 6.21.5.3 Other reasons to extend <tt class="module">optparse</tt> | |
57 | </H3> | |
58 | ||
59 | <P> | |
60 | Adding new types and new actions are the big, obvious reasons why you | |
61 | might want to extend <tt class="module">optparse</tt>. I can think of at least two other areas to | |
62 | play with. | |
63 | ||
64 | <P> | |
65 | First, the simple one: OptionParser tries to be helpful by calling | |
66 | <tt class="function">sys.exit()</tt> when appropriate, i.e. when there's an error on the | |
67 | command line or when the user requests help. In the former case, the | |
68 | traditional course of letting the script crash with a traceback is | |
69 | unacceptable; it will make users think there's a bug in your script when | |
70 | they make a command-line error. In the latter case, there's generally | |
71 | not much point in carrying on after printing a help message. | |
72 | ||
73 | <P> | |
74 | If this behaviour bothers you, it shouldn't be too hard to ``fix'' it. | |
75 | You'll have to | |
76 | ||
77 | <DL COMPACT> | |
78 | <DT> | |
79 | ||
80 | 1) | |
81 | <DD> | |
82 | subclass OptionParser and override <tt class="method">error()</tt> | |
83 | ||
84 | <P> | |
85 | <DT> | |
86 | ||
87 | 2) | |
88 | <DD> | |
89 | subclass Option and override <tt class="method">take_action()</tt>--you'll | |
90 | need to provide your own handling of the <tt class="member">help</tt> action that | |
91 | doesn't call <tt class="function">sys.exit()</tt> | |
92 | ||
93 | <P> | |
94 | </DD> | |
95 | </DL> | |
96 | ||
97 | <P> | |
98 | The second, much more complex, possibility is to override the | |
99 | command-line syntax implemented by <tt class="module">optparse</tt>. In this case, you'd leave the | |
100 | whole machinery of option actions and types alone, but rewrite the code | |
101 | that processes <var>sys.argv</var>. You'll need to subclass OptionParser in any | |
102 | case; depending on how radical a rewrite you want, you'll probably need | |
103 | to override one or all of <tt class="method">parse_args()</tt>, <tt class="method">_process_long_opt()</tt>, and | |
104 | <tt class="method">_process_short_opts()</tt>. | |
105 | ||
106 | <P> | |
107 | Both of these are left as an exercise for the reader. I have not tried | |
108 | to implement either myself, since I'm quite happy with <tt class="module">optparse</tt>'s default | |
109 | behaviour (naturally). | |
110 | ||
111 | <P> | |
112 | Happy hacking, and don't forget: Use the Source, Luke. | |
113 | ||
114 | <DIV CLASS="navigation"> | |
115 | <div class='online-navigation'> | |
116 | <p></p><hr /> | |
117 | <table align="center" width="100%" cellpadding="0" cellspacing="2"> | |
118 | <tr> | |
119 | <td class='online-navigation'><a rel="prev" title="6.21.5.2 Adding new actions" | |
120 | href="optparse-adding-new-actions.html"><img src='../icons/previous.png' | |
121 | border='0' height='32' alt='Previous Page' width='32' /></A></td> | |
122 | <td class='online-navigation'><a rel="parent" title="6.21.5 Extending optparse" | |
123 | href="optparse-extending-optparse.html"><img src='../icons/up.png' | |
124 | border='0' height='32' alt='Up One Level' width='32' /></A></td> | |
125 | <td class='online-navigation'><a rel="next" title="6.22 tempfile " | |
126 | href="module-tempfile.html"><img src='../icons/next.png' | |
127 | border='0' height='32' alt='Next Page' width='32' /></A></td> | |
128 | <td align="center" width="100%">Python Library Reference</td> | |
129 | <td class='online-navigation'><a rel="contents" title="Table of Contents" | |
130 | href="contents.html"><img src='../icons/contents.png' | |
131 | border='0' height='32' alt='Contents' width='32' /></A></td> | |
132 | <td class='online-navigation'><a href="modindex.html" title="Module Index"><img src='../icons/modules.png' | |
133 | border='0' height='32' alt='Module Index' width='32' /></a></td> | |
134 | <td class='online-navigation'><a rel="index" title="Index" | |
135 | href="genindex.html"><img src='../icons/index.png' | |
136 | border='0' height='32' alt='Index' width='32' /></A></td> | |
137 | </tr></table> | |
138 | <div class='online-navigation'> | |
139 | <b class="navlabel">Previous:</b> | |
140 | <a class="sectref" rel="prev" href="optparse-adding-new-actions.html">6.21.5.2 Adding new actions</A> | |
141 | <b class="navlabel">Up:</b> | |
142 | <a class="sectref" rel="parent" href="optparse-extending-optparse.html">6.21.5 Extending optparse</A> | |
143 | <b class="navlabel">Next:</b> | |
144 | <a class="sectref" rel="next" href="module-tempfile.html">6.22 tempfile </A> | |
145 | </div> | |
146 | </div> | |
147 | <hr /> | |
148 | <span class="release-info">Release 2.4.2, documentation updated on 28 September 2005.</span> | |
149 | </DIV> | |
150 | <!--End of Navigation Panel--> | |
151 | <ADDRESS> | |
152 | See <i><a href="about.html">About this document...</a></i> for information on suggesting changes. | |
153 | </ADDRESS> | |
154 | </BODY> | |
155 | </HTML> |