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| 55 | <H3><A NAME="SECTION0082135000000000000000"></A><A NAME="optparse-option-attributes"></A> |
| 56 | <BR> |
| 57 | 6.21.3.5 Option attributes |
| 58 | </H3> |
| 59 | |
| 60 | <P> |
| 61 | The following option attributes may be passed as keyword arguments |
| 62 | to <code>parser.add_option()</code>. If you pass an option attribute |
| 63 | that is not relevant to a particular option, or fail to pass a required |
| 64 | option attribute, <tt class="module">optparse</tt> raises OptionError. |
| 65 | |
| 66 | <UL> |
| 67 | <LI> |
| 68 | <tt class="member">action</tt> (default: <code>"store"</code>) |
| 69 | |
| 70 | <P> |
| 71 | Determines <tt class="module">optparse</tt>'s behaviour when this option is seen on the command |
| 72 | line; the available options are documented above. |
| 73 | |
| 74 | <P> |
| 75 | </LI> |
| 76 | <LI> |
| 77 | <tt class="member">type</tt> (default: <code>"string"</code>) |
| 78 | |
| 79 | <P> |
| 80 | The argument type expected by this option (e.g., <code>"string"</code> or |
| 81 | <code>"int"</code>); the available option types are documented below. |
| 82 | |
| 83 | <P> |
| 84 | </LI> |
| 85 | <LI> |
| 86 | <tt class="member">dest</tt> (default: derived from option strings) |
| 87 | |
| 88 | <P> |
| 89 | If the option's action implies writing or modifying a value somewhere, |
| 90 | this tells <tt class="module">optparse</tt> where to write it: <tt class="member">dest</tt> names an attribute of the |
| 91 | <code>options</code> object that <tt class="module">optparse</tt> builds as it parses the command line. |
| 92 | |
| 93 | <P> |
| 94 | </LI> |
| 95 | <LI> |
| 96 | <code>default</code> (deprecated) |
| 97 | |
| 98 | <P> |
| 99 | The value to use for this option's destination if the option is not |
| 100 | seen on the command line. Deprecated; use <code>parser.set_defaults()</code> |
| 101 | instead. |
| 102 | |
| 103 | <P> |
| 104 | </LI> |
| 105 | <LI> |
| 106 | <code>nargs</code> (default: 1) |
| 107 | |
| 108 | <P> |
| 109 | How many arguments of type <tt class="member">type</tt> should be consumed when this |
| 110 | option is seen. If > 1, <tt class="module">optparse</tt> will store a tuple of values to |
| 111 | <tt class="member">dest</tt>. |
| 112 | |
| 113 | <P> |
| 114 | </LI> |
| 115 | <LI> |
| 116 | <code>const</code> |
| 117 | |
| 118 | <P> |
| 119 | For actions that store a constant value, the constant value to store. |
| 120 | |
| 121 | <P> |
| 122 | </LI> |
| 123 | <LI> |
| 124 | <code>choices</code> |
| 125 | |
| 126 | <P> |
| 127 | For options of type <code>"choice"</code>, the list of strings the user |
| 128 | may choose from. |
| 129 | |
| 130 | <P> |
| 131 | </LI> |
| 132 | <LI> |
| 133 | <code>callback</code> |
| 134 | |
| 135 | <P> |
| 136 | For options with action <code>"callback"</code>, the callable to call when this |
| 137 | option is seen. See section <A href="optparse-option-callbacks.html#optparse-option-callbacks">6.21.4</A>, Option Callbacks for detail on the arguments |
| 138 | passed to <code>callable</code>. |
| 139 | |
| 140 | <P> |
| 141 | </LI> |
| 142 | <LI> |
| 143 | <code>callback_args</code>, <code>callback_kwargs</code> |
| 144 | |
| 145 | <P> |
| 146 | Additional positional and keyword arguments to pass to <code>callback</code> |
| 147 | after the four standard callback arguments. |
| 148 | |
| 149 | <P> |
| 150 | </LI> |
| 151 | <LI> |
| 152 | <tt class="member">help</tt> |
| 153 | |
| 154 | <P> |
| 155 | Help text to print for this option when listing all available options |
| 156 | after the user supplies a <tt class="member">help</tt> option (such as <code>"-help"</code>). |
| 157 | If no help text is supplied, the option will be listed without help |
| 158 | text. To hide this option, use the special value <code>SUPPRESS_HELP</code>. |
| 159 | |
| 160 | <P> |
| 161 | </LI> |
| 162 | <LI> |
| 163 | <code>metavar</code> (default: derived from option strings) |
| 164 | |
| 165 | <P> |
| 166 | Stand-in for the option argument(s) to use when printing help text. |
| 167 | See section <A href="optparse-tutorial.html#optparse-tutorial">6.21.2</A>, the tutorial for an example. |
| 168 | |
| 169 | <P> |
| 170 | </LI> |
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