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| 55 | <H3><A NAME="SECTION0082122000000000000000"></A><A NAME="optparse-store-action"></A> |
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| 57 | 6.21.2.2 The store action |
| 58 | </H3> |
| 59 | |
| 60 | <P> |
| 61 | The most common option action is <code>store</code>, which tells <tt class="module">optparse</tt> to take |
| 62 | the next argument (or the remainder of the current argument), ensure |
| 63 | that it is of the correct type, and store it to your chosen destination. |
| 64 | |
| 65 | <P> |
| 66 | For example: |
| 67 | <div class="verbatim"><pre> |
| 68 | parser.add_option("-f", "--file", |
| 69 | action="store", type="string", dest="filename") |
| 70 | </pre></div> |
| 71 | |
| 72 | <P> |
| 73 | Now let's make up a fake command line and ask <tt class="module">optparse</tt> to parse it: |
| 74 | <div class="verbatim"><pre> |
| 75 | args = ["-f", "foo.txt"] |
| 76 | (options, args) = parser.parse_args(args) |
| 77 | </pre></div> |
| 78 | |
| 79 | <P> |
| 80 | When <tt class="module">optparse</tt> sees the option string <code>"-f"</code>, it consumes the next |
| 81 | argument, <code>"foo.txt"</code>, and stores it in <code>options.filename</code>. So, |
| 82 | after this call to <tt class="method">parse_args()</tt>, <code>options.filename</code> is |
| 83 | <code>"foo.txt"</code>. |
| 84 | |
| 85 | <P> |
| 86 | Some other option types supported by <tt class="module">optparse</tt> are <code>int</code> and <code>float</code>. |
| 87 | Here's an option that expects an integer argument: |
| 88 | <div class="verbatim"><pre> |
| 89 | parser.add_option("-n", type="int", dest="num") |
| 90 | </pre></div> |
| 91 | |
| 92 | <P> |
| 93 | Note that this option has no long option string, which is perfectly |
| 94 | acceptable. Also, there's no explicit action, since the default is |
| 95 | <code>store</code>. |
| 96 | |
| 97 | <P> |
| 98 | Let's parse another fake command-line. This time, we'll jam the option |
| 99 | argument right up against the option: since <code>"-n42"</code> (one argument) is |
| 100 | equivalent to <code>"-n 42"</code> (two arguments), the code |
| 101 | <div class="verbatim"><pre> |
| 102 | (options, args) = parser.parse_args(["-n42"]) |
| 103 | print options.num |
| 104 | </pre></div> |
| 105 | |
| 106 | <P> |
| 107 | will print <code>"42"</code>. |
| 108 | |
| 109 | <P> |
| 110 | If you don't specify a type, <tt class="module">optparse</tt> assumes <code>string</code>. Combined with the |
| 111 | fact that the default action is <code>store</code>, that means our first example |
| 112 | can be a lot shorter: |
| 113 | <div class="verbatim"><pre> |
| 114 | parser.add_option("-f", "--file", dest="filename") |
| 115 | </pre></div> |
| 116 | |
| 117 | <P> |
| 118 | If you don't supply a destination, <tt class="module">optparse</tt> figures out a sensible default |
| 119 | from the option strings: if the first long option string is |
| 120 | <code>"-foo-bar"</code>, then the default destination is <code>foo_bar</code>. If there |
| 121 | are no long option strings, <tt class="module">optparse</tt> looks at the first short option |
| 122 | string: the default destination for <code>"-f"</code> is <code>f</code>. |
| 123 | |
| 124 | <P> |
| 125 | <tt class="module">optparse</tt> also includes built-in <code>long</code> and <code>complex</code> types. Adding |
| 126 | types is covered in section <A HREF="#optparse-extending"><tex2html_cross_ref_visible_mark></A>, Extending <tt class="module">optparse</tt>. |
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