projects / OpenSPARC-T2-SAM / blame
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| 53 | ||
| 54 | <H2><A NAME="SECTION0051140000000000000000"></A><A NAME="inspect-stack"></A> | |
| 55 | <BR> | |
| 56 | 3.11.4 The interpreter stack | |
| 57 | ||
| 58 | </H2> | |
| 59 | ||
| 60 | <P> | |
| 61 | When the following functions return ``frame records,'' each record | |
| 62 | is a tuple of six items: the frame object, the filename, | |
| 63 | the line number of the current line, the function name, a list of | |
| 64 | lines of context from the source code, and the index of the current | |
| 65 | line within that list. | |
| 66 | ||
| 67 | <P> | |
| 68 | <div class="warning"><b class="label">Warning:</b> | |
| 69 | ||
| 70 | Keeping references to frame objects, as found in | |
| 71 | the first element of the frame records these functions return, can | |
| 72 | cause your program to create reference cycles. Once a reference cycle | |
| 73 | has been created, the lifespan of all objects which can be accessed | |
| 74 | from the objects which form the cycle can become much longer even if | |
| 75 | Python's optional cycle detector is enabled. If such cycles must be | |
| 76 | created, it is important to ensure they are explicitly broken to avoid | |
| 77 | the delayed destruction of objects and increased memory consumption | |
| 78 | which occurs. | |
| 79 | ||
| 80 | <P> | |
| 81 | Though the cycle detector will catch these, destruction of the frames | |
| 82 | (and local variables) can be made deterministic by removing the cycle | |
| 83 | in a <tt class="keyword">finally</tt> clause. This is also important if the cycle | |
| 84 | detector was disabled when Python was compiled or using | |
| 85 | <tt class="function"><tt class="module"><a href="module-gc.html">gc</a></tt>.disable()</tt>. For example: | |
| 86 | ||
| 87 | <P> | |
| 88 | <div class="verbatim"><pre> | |
| 89 | def handle_stackframe_without_leak(): | |
| 90 | frame = inspect.currentframe() | |
| 91 | try: | |
| 92 | # do something with the frame | |
| 93 | finally: | |
| 94 | del frame | |
| 95 | </pre></div> | |
| 96 | </div> | |
| 97 | ||
| 98 | <P> | |
| 99 | The optional <var>context</var> argument supported by most of these | |
| 100 | functions specifies the number of lines of context to return, which | |
| 101 | are centered around the current line. | |
| 102 | ||
| 103 | <P> | |
| 104 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> | |
| 105 | <td><nobr><b><tt id='l2h-598' xml:id='l2h-598' class="function">getframeinfo</tt></b>(</nobr></td> | |
| 106 | <td><var>frame</var><big>[</big><var>, context</var><big>]</big><var></var>)</td></tr></table></dt> | |
| 107 | <dd> | |
| 108 | Get information about a frame or traceback object. A 5-tuple | |
| 109 | is returned, the last five elements of the frame's frame record. | |
| 110 | </dl> | |
| 111 | ||
| 112 | <P> | |
| 113 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> | |
| 114 | <td><nobr><b><tt id='l2h-599' xml:id='l2h-599' class="function">getouterframes</tt></b>(</nobr></td> | |
| 115 | <td><var>frame</var><big>[</big><var>, context</var><big>]</big><var></var>)</td></tr></table></dt> | |
| 116 | <dd> | |
| 117 | Get a list of frame records for a frame and all outer frames. These | |
| 118 | frames represent the calls that lead to the creation of <var>frame</var>. | |
| 119 | The first entry in the returned list represents <var>frame</var>; the | |
| 120 | last entry represents the outermost call on <var>frame</var>'s stack. | |
| 121 | </dl> | |
| 122 | ||
| 123 | <P> | |
| 124 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> | |
| 125 | <td><nobr><b><tt id='l2h-600' xml:id='l2h-600' class="function">getinnerframes</tt></b>(</nobr></td> | |
| 126 | <td><var>traceback</var><big>[</big><var>, context</var><big>]</big><var></var>)</td></tr></table></dt> | |
| 127 | <dd> | |
| 128 | Get a list of frame records for a traceback's frame and all inner | |
| 129 | frames. These frames represent calls made as a consequence of | |
| 130 | <var>frame</var>. The first entry in the list represents | |
| 131 | <var>traceback</var>; the last entry represents where the exception was | |
| 132 | raised. | |
| 133 | </dl> | |
| 134 | ||
| 135 | <P> | |
| 136 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> | |
| 137 | <td><nobr><b><tt id='l2h-601' xml:id='l2h-601' class="function">currentframe</tt></b>(</nobr></td> | |
| 138 | <td><var></var>)</td></tr></table></dt> | |
| 139 | <dd> | |
| 140 | Return the frame object for the caller's stack frame. | |
| 141 | </dl> | |
| 142 | ||
| 143 | <P> | |
| 144 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> | |
| 145 | <td><nobr><b><tt id='l2h-602' xml:id='l2h-602' class="function">stack</tt></b>(</nobr></td> | |
| 146 | <td><var></var><big>[</big><var>context</var><big>]</big><var></var>)</td></tr></table></dt> | |
| 147 | <dd> | |
| 148 | Return a list of frame records for the caller's stack. The first | |
| 149 | entry in the returned list represents the caller; the last entry | |
| 150 | represents the outermost call on the stack. | |
| 151 | </dl> | |
| 152 | ||
| 153 | <P> | |
| 154 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> | |
| 155 | <td><nobr><b><tt id='l2h-603' xml:id='l2h-603' class="function">trace</tt></b>(</nobr></td> | |
| 156 | <td><var></var><big>[</big><var>context</var><big>]</big><var></var>)</td></tr></table></dt> | |
| 157 | <dd> | |
| 158 | Return a list of frame records for the stack between the current | |
| 159 | frame and the frame in which an exception currently being handled | |
| 160 | was raised in. The first entry in the list represents the caller; | |
| 161 | the last entry represents where the exception was raised. | |
| 162 | </dl> | |
| 163 | ||
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| 187 | </tr></table> | |
| 188 | <div class='online-navigation'> | |
| 189 | <b class="navlabel">Previous:</b> | |
| 190 | <a class="sectref" rel="prev" href="inspect-classes-functions.html">3.11.3 Classes and functions</A> | |
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| 195 | </div> | |
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| 198 | <span class="release-info">Release 2.4.2, documentation updated on 28 September 2005.</span> | |
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