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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. |
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