projects / OpenSPARC-T2-DV / blame
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| 52 | ||
| 53 | <H2><A NAME="SECTION004230000000000000000"> | |
| 54 | 2.2.3 Attribute Management</A> | |
| 55 | </H2> | |
| 56 | ||
| 57 | <P> | |
| 58 | For every object which can support attributes, the corresponding type | |
| 59 | must provide the functions that control how the attributes are | |
| 60 | resolved. There needs to be a function which can retrieve attributes | |
| 61 | (if any are defined), and another to set attributes (if setting | |
| 62 | attributes is allowed). Removing an attribute is a special case, for | |
| 63 | which the new value passed to the handler is <tt class="constant">NULL</tt>. | |
| 64 | ||
| 65 | <P> | |
| 66 | Python supports two pairs of attribute handlers; a type that supports | |
| 67 | attributes only needs to implement the functions for one pair. The | |
| 68 | difference is that one pair takes the name of the attribute as a | |
| 69 | <tt class="ctype">char*</tt>, while the other accepts a <tt class="ctype">PyObject*</tt>. Each type | |
| 70 | can use whichever pair makes more sense for the implementation's | |
| 71 | convenience. | |
| 72 | ||
| 73 | <P> | |
| 74 | <div class="verbatim"><pre> | |
| 75 | getattrfunc tp_getattr; /* char * version */ | |
| 76 | setattrfunc tp_setattr; | |
| 77 | /* ... */ | |
| 78 | getattrofunc tp_getattrofunc; /* PyObject * version */ | |
| 79 | setattrofunc tp_setattrofunc; | |
| 80 | </pre></div> | |
| 81 | ||
| 82 | <P> | |
| 83 | If accessing attributes of an object is always a simple operation | |
| 84 | (this will be explained shortly), there are generic implementations | |
| 85 | which can be used to provide the <tt class="ctype">PyObject*</tt> version of the | |
| 86 | attribute management functions. The actual need for type-specific | |
| 87 | attribute handlers almost completely disappeared starting with Python | |
| 88 | 2.2, though there are many examples which have not been updated to use | |
| 89 | some of the new generic mechanism that is available. | |
| 90 | ||
| 91 | <P> | |
| 92 | ||
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| 97 | ||
| 98 | <UL CLASS="ChildLinks"> | |
| 99 | <LI><A href="node29.html">2.2.3.1 Generic Attribute Management</a> | |
| 100 | <LI><A href="node30.html">2.2.3.2 Type-specific Attribute Management</a> | |
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| 119 | <td align="center" width="100%">Extending and Embedding the Python Interpreter</td> | |
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| 138 | <span class="release-info">Release 2.4.2, documentation updated on 28 September 2005.</span> | |
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