projects / OpenSPARC-T2-SAM / blame
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| 17 | <title>1.2 Objects, Types and Reference Counts </title> | |
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| 54 | ||
| 55 | <H1><A NAME="SECTION003200000000000000000"></A><A NAME="objects"></A> | |
| 56 | <BR> | |
| 57 | 1.2 Objects, Types and Reference Counts | |
| 58 | </H1> | |
| 59 | ||
| 60 | <P> | |
| 61 | Most Python/C API functions have one or more arguments as well as a | |
| 62 | return value of type <tt class="ctype">PyObject*</tt>. This type is a pointer | |
| 63 | to an opaque data type representing an arbitrary Python | |
| 64 | object. Since all Python object types are treated the same way by the | |
| 65 | Python language in most situations (e.g., assignments, scope rules, | |
| 66 | and argument passing), it is only fitting that they should be | |
| 67 | represented by a single C type. Almost all Python objects live on the | |
| 68 | heap: you never declare an automatic or static variable of type | |
| 69 | <tt class="ctype">PyObject</tt>, only pointer variables of type <tt class="ctype">PyObject*</tt> can | |
| 70 | be declared. The sole exception are the type objects<a id='l2h-9' xml:id='l2h-9'></a>; | |
| 71 | since these must never be deallocated, they are typically static | |
| 72 | <tt class="ctype">PyTypeObject</tt> objects. | |
| 73 | ||
| 74 | <P> | |
| 75 | All Python objects (even Python integers) have a <i class="dfn">type</i> and a | |
| 76 | <i class="dfn">reference count</i>. An object's type determines what kind of object | |
| 77 | it is (e.g., an integer, a list, or a user-defined function; there are | |
| 78 | many more as explained in the <em class="citetitle"><a | |
| 79 | href="../ref/ref.html" | |
| 80 | title="Python | |
| 81 | Reference Manual" | |
| 82 | >Python | |
| 83 | Reference Manual</a></em>). For each of the well-known types there is a macro | |
| 84 | to check whether an object is of that type; for instance, | |
| 85 | "<tt class="samp">PyList_Check(<var>a</var>)</tt>" is true if (and only if) the object | |
| 86 | pointed to by <var>a</var> is a Python list. | |
| 87 | ||
| 88 | <P> | |
| 89 | ||
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| 91 | <div class='online-navigation'> | |
| 92 | <!--Table of Child-Links--> | |
| 93 | <A NAME="CHILD_LINKS"><STRONG>Subsections</STRONG></a> | |
| 94 | ||
| 95 | <UL CLASS="ChildLinks"> | |
| 96 | <LI><A href="refcounts.html">1.2.1 Reference Counts</a> | |
| 97 | <UL> | |
| 98 | <LI><A href="refcountDetails.html">1.2.1.1 Reference Count Details</a> | |
| 99 | </ul> | |
| 100 | <LI><A href="types.html">1.2.2 Types</a> | |
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| 118 | border='0' height='32' alt='Next Page' width='32' /></A></td> | |
| 119 | <td align="center" width="100%">Python/C API Reference Manual</td> | |
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| 127 | border='0' height='32' alt='Index' width='32' /></A></td> | |
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| 130 | <b class="navlabel">Previous:</b> | |
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| 135 | <a class="sectref" rel="next" href="refcounts.html">1.2.1 Reference Counts</A> | |
| 136 | </div> | |
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| 139 | <span class="release-info">Release 2.4.2, documentation updated on 28 September 2005.</span> | |
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