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52 | <H1><A NAME="SECTION00104600000000000000000"> | |
53 | 10.46 Creating a new Distutils command</A> | |
54 | </H1> | |
55 | ||
56 | <P> | |
57 | This section outlines the steps to create a new Distutils command. | |
58 | ||
59 | <P> | |
60 | A new command lives in a module in the <tt class="module">distutils.command</tt> | |
61 | package. There is a sample template in that directory called | |
62 | <span class="file">command_template</span>. Copy this file to a new module with the | |
63 | same name as the new command you're implementing. This module should | |
64 | implement a class with the same name as the module (and the command). | |
65 | So, for instance, to create the command <code>peel_banana</code> (so that users | |
66 | can run "<tt class="samp">setup.py peel_banana</tt>"), you'd copy <span class="file">command_template</span> | |
67 | to <span class="file">distutils/command/peel_banana.py</span>, then edit it so that it's | |
68 | implementing the class <tt class="class">peel_banana</tt>, a subclass of | |
69 | <tt class="class">distutils.cmd.Command</tt>. | |
70 | ||
71 | <P> | |
72 | Subclasses of <tt class="class">Command</tt> must define the following methods. | |
73 | ||
74 | <P> | |
75 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> | |
76 | <td><nobr><b><tt id='l2h-148' xml:id='l2h-148' class="method">initialize_options()</tt></b>(</nobr></td> | |
77 | <td><var>S</var>)</td></tr></table></dt> | |
78 | <dd>et default values for all the options that this command | |
79 | supports. Note that these defaults may be overridden by other | |
80 | commands, by the setup script, by config files, or by the | |
81 | command-line. Thus, this is not the place to code dependencies | |
82 | between options; generally, <tt class="method">initialize_options()</tt> implementations | |
83 | are just a bunch of "<tt class="samp">self.foo = None</tt>" assignments. | |
84 | </dl> | |
85 | ||
86 | <P> | |
87 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> | |
88 | <td><nobr><b><tt id='l2h-149' xml:id='l2h-149' class="method">finalize_options</tt></b>(</nobr></td> | |
89 | <td><var></var>)</td></tr></table></dt> | |
90 | <dd> | |
91 | Set final values for all the options that this command supports. | |
92 | This is always called as late as possible, ie. after any option | |
93 | assignments from the command-line or from other commands have been | |
94 | done. Thus, this is the place to to code option dependencies: if | |
95 | <var>foo</var> depends on <var>bar</var>, then it is safe to set <var>foo</var> from | |
96 | <var>bar</var> as long as <var>foo</var> still has the same value it was assigned in | |
97 | <tt class="method">initialize_options()</tt>. | |
98 | </dl> | |
99 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> | |
100 | <td><nobr><b><tt id='l2h-150' xml:id='l2h-150' class="method">run</tt></b>(</nobr></td> | |
101 | <td><var></var>)</td></tr></table></dt> | |
102 | <dd> | |
103 | A command's raison d'etre: carry out the action it exists to | |
104 | perform, controlled by the options initialized in | |
105 | <tt class="method">initialize_options()</tt>, customized by other commands, the setup | |
106 | script, the command-line, and config files, and finalized in | |
107 | <tt class="method">finalize_options()</tt>. All terminal output and filesystem | |
108 | interaction should be done by <tt class="method">run()</tt>. | |
109 | </dl> | |
110 | ||
111 | <P> | |
112 | <var>sub_commands</var> formalizes the notion of a ``family'' of commands, | |
113 | eg. <code>install</code> as the parent with sub-commands <code>install_lib</code>, | |
114 | <code>install_headers</code>, etc. The parent of a family of commands | |
115 | defines <var>sub_commands</var> as a class attribute; it's a list of | |
116 | 2-tuples "<tt class="samp">(command_name, predicate)</tt>", with <var>command_name</var> a string | |
117 | and <var>predicate</var> an unbound method, a string or None. | |
118 | <var>predicate</var> is a method of the parent command that | |
119 | determines whether the corresponding command is applicable in the | |
120 | current situation. (Eg. we <code>install_headers</code> is only applicable if | |
121 | we have any C header files to install.) If <var>predicate</var> is None, | |
122 | that command is always applicable. | |
123 | ||
124 | <P> | |
125 | <var>sub_commands</var> is usually defined at the *end* of a class, because | |
126 | predicates can be unbound methods, so they must already have been | |
127 | defined. The canonical example is the <code class="du-command">install</code> command. | |
128 | ||
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