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55 | <H3><A NAME="SECTION0043104000000000000000"></A><A NAME="typesmethods"></A> | |
56 | <BR> | |
57 | 2.3.10.4 Methods | |
58 | </H3> | |
59 | <a id='l2h-260' xml:id='l2h-260'></a> | |
60 | <P> | |
61 | Methods are functions that are called using the attribute notation. | |
62 | There are two flavors: built-in methods (such as <tt class="method">append()</tt> on | |
63 | lists) and class instance methods. Built-in methods are described | |
64 | with the types that support them. | |
65 | ||
66 | <P> | |
67 | The implementation adds two special read-only attributes to class | |
68 | instance methods: <code><var>m</var>.im_self</code> is the object on which the | |
69 | method operates, and <code><var>m</var>.im_func</code> is the function | |
70 | implementing the method. Calling <code><var>m</var>(<var>arg-1</var>, | |
71 | <var>arg-2</var>, ..., <var>arg-n</var>)</code> is completely equivalent to | |
72 | calling <code><var>m</var>.im_func(<var>m</var>.im_self, <var>arg-1</var>, | |
73 | <var>arg-2</var>, ..., <var>arg-n</var>)</code>. | |
74 | ||
75 | <P> | |
76 | Class instance methods are either <em>bound</em> or <em>unbound</em>, | |
77 | referring to whether the method was accessed through an instance or a | |
78 | class, respectively. When a method is unbound, its <code>im_self</code> | |
79 | attribute will be <code>None</code> and if called, an explicit <code>self</code> | |
80 | object must be passed as the first argument. In this case, | |
81 | <code>self</code> must be an instance of the unbound method's class (or a | |
82 | subclass of that class), otherwise a <code>TypeError</code> is raised. | |
83 | ||
84 | <P> | |
85 | Like function objects, methods objects support getting | |
86 | arbitrary attributes. However, since method attributes are actually | |
87 | stored on the underlying function object (<code>meth.im_func</code>), | |
88 | setting method attributes on either bound or unbound methods is | |
89 | disallowed. Attempting to set a method attribute results in a | |
90 | <code>TypeError</code> being raised. In order to set a method attribute, | |
91 | you need to explicitly set it on the underlying function object: | |
92 | ||
93 | <P> | |
94 | <div class="verbatim"><pre> | |
95 | class C: | |
96 | def method(self): | |
97 | pass | |
98 | ||
99 | c = C() | |
100 | c.method.im_func.whoami = 'my name is c' | |
101 | </pre></div> | |
102 | ||
103 | <P> | |
104 | See the <em class="citetitle"><a | |
105 | href="../ref/ref.html" | |
106 | title="Python Reference Manual" | |
107 | >Python Reference Manual</a></em> for more | |
108 | information. | |
109 | ||
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