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| 53 | 2.2.6 More Suggestions</A> |
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| 55 | |
| 56 | <P> |
| 57 | Remember that you can omit most of these functions, in which case you |
| 58 | provide <code>0</code> as a value. There are type definitions for each of |
| 59 | the functions you must provide. They are in <span class="file">object.h</span> in the |
| 60 | Python include directory that comes with the source distribution of |
| 61 | Python. |
| 62 | |
| 63 | <P> |
| 64 | In order to learn how to implement any specific method for your new |
| 65 | data type, do the following: Download and unpack the Python source |
| 66 | distribution. Go the <span class="file">Objects</span> directory, then search the |
| 67 | C source files for <code>tp_</code> plus the function you want (for |
| 68 | example, <code>tp_print</code> or <code>tp_compare</code>). You will find |
| 69 | examples of the function you want to implement. |
| 70 | |
| 71 | <P> |
| 72 | When you need to verify that an object is an instance of the type |
| 73 | you are implementing, use the <tt class="cfunction">PyObject_TypeCheck</tt> function. |
| 74 | A sample of its use might be something like the following: |
| 75 | |
| 76 | <P> |
| 77 | <div class="verbatim"><pre> |
| 78 | if (! PyObject_TypeCheck(some_object, &MyType)) { |
| 79 | PyErr_SetString(PyExc_TypeError, "arg #1 not a mything"); |
| 80 | return NULL; |
| 81 | } |
| 82 | </pre></div> |
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| 117 | <span class="release-info">Release 2.4.2, documentation updated on 28 September 2005.</span> |
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