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| 55 | <H1><A NAME="SECTION00201000000000000000000"> |
| 56 | 18.10 <tt class="module">dis</tt> -- |
| 57 | Disassembler for Python byte code</A> |
| 58 | </H1> |
| 59 | |
| 60 | <P> |
| 61 | <A NAME="module-dis"></A> |
| 62 | |
| 63 | <P> |
| 64 | The <tt class="module">dis</tt> module supports the analysis of Python byte code by |
| 65 | disassembling it. Since there is no Python assembler, this module |
| 66 | defines the Python assembly language. The Python byte code which |
| 67 | this module takes as an input is defined in the file |
| 68 | <span class="file">Include/opcode.h</span> and used by the compiler and the interpreter. |
| 69 | |
| 70 | <P> |
| 71 | Example: Given the function <tt class="function">myfunc</tt>: |
| 72 | |
| 73 | <P> |
| 74 | <div class="verbatim"><pre> |
| 75 | def myfunc(alist): |
| 76 | return len(alist) |
| 77 | </pre></div> |
| 78 | |
| 79 | <P> |
| 80 | the following command can be used to get the disassembly of |
| 81 | <tt class="function">myfunc()</tt>: |
| 82 | |
| 83 | <P> |
| 84 | <div class="verbatim"><pre> |
| 85 | >>> dis.dis(myfunc) |
| 86 | 2 0 LOAD_GLOBAL 0 (len) |
| 87 | 3 LOAD_FAST 0 (alist) |
| 88 | 6 CALL_FUNCTION 1 |
| 89 | 9 RETURN_VALUE |
| 90 | 10 LOAD_CONST 0 (None) |
| 91 | 13 RETURN_VALUE |
| 92 | </pre></div> |
| 93 | |
| 94 | <P> |
| 95 | (The ``2'' is a line number). |
| 96 | |
| 97 | <P> |
| 98 | The <tt class="module">dis</tt> module defines the following functions and constants: |
| 99 | |
| 100 | <P> |
| 101 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 102 | <td><nobr><b><tt id='l2h-5001' xml:id='l2h-5001' class="function">dis</tt></b>(</nobr></td> |
| 103 | <td><var></var><big>[</big><var>bytesource</var><big>]</big><var></var>)</td></tr></table></dt> |
| 104 | <dd> |
| 105 | Disassemble the <var>bytesource</var> object. <var>bytesource</var> can denote |
| 106 | either a module, a class, a method, a function, or a code object. |
| 107 | For a module, it disassembles all functions. For a class, |
| 108 | it disassembles all methods. For a single code sequence, it prints |
| 109 | one line per byte code instruction. If no object is provided, it |
| 110 | disassembles the last traceback. |
| 111 | </dl> |
| 112 | |
| 113 | <P> |
| 114 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 115 | <td><nobr><b><tt id='l2h-5002' xml:id='l2h-5002' class="function">distb</tt></b>(</nobr></td> |
| 116 | <td><var></var><big>[</big><var>tb</var><big>]</big><var></var>)</td></tr></table></dt> |
| 117 | <dd> |
| 118 | Disassembles the top-of-stack function of a traceback, using the last |
| 119 | traceback if none was passed. The instruction causing the exception |
| 120 | is indicated. |
| 121 | </dl> |
| 122 | |
| 123 | <P> |
| 124 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 125 | <td><nobr><b><tt id='l2h-5003' xml:id='l2h-5003' class="function">disassemble</tt></b>(</nobr></td> |
| 126 | <td><var>code</var><big>[</big><var>, lasti</var><big>]</big><var></var>)</td></tr></table></dt> |
| 127 | <dd> |
| 128 | Disassembles a code object, indicating the last instruction if <var>lasti</var> |
| 129 | was provided. The output is divided in the following columns: |
| 130 | |
| 131 | <P> |
| 132 | |
| 133 | <OL> |
| 134 | <LI>the line number, for the first instruction of each line |
| 135 | </LI> |
| 136 | <LI>the current instruction, indicated as "<tt class="samp">--></tt>", |
| 137 | </LI> |
| 138 | <LI>a labelled instruction, indicated with "<tt class="samp">><code>></code></tt>", |
| 139 | </LI> |
| 140 | <LI>the address of the instruction, |
| 141 | </LI> |
| 142 | <LI>the operation code name, |
| 143 | </LI> |
| 144 | <LI>operation parameters, and |
| 145 | </LI> |
| 146 | <LI>interpretation of the parameters in parentheses. |
| 147 | </LI> |
| 148 | </OL> |
| 149 | |
| 150 | <P> |
| 151 | The parameter interpretation recognizes local and global |
| 152 | variable names, constant values, branch targets, and compare |
| 153 | operators. |
| 154 | </dl> |
| 155 | |
| 156 | <P> |
| 157 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 158 | <td><nobr><b><tt id='l2h-5004' xml:id='l2h-5004' class="function">disco</tt></b>(</nobr></td> |
| 159 | <td><var>code</var><big>[</big><var>, lasti</var><big>]</big><var></var>)</td></tr></table></dt> |
| 160 | <dd> |
| 161 | A synonym for disassemble. It is more convenient to type, and kept |
| 162 | for compatibility with earlier Python releases. |
| 163 | </dl> |
| 164 | |
| 165 | <P> |
| 166 | <dl><dt><b><tt id='l2h-5005' xml:id='l2h-5005'>opname</tt></b></dt> |
| 167 | <dd> |
| 168 | Sequence of operation names, indexable using the byte code. |
| 169 | </dd></dl> |
| 170 | |
| 171 | <P> |
| 172 | <dl><dt><b><tt id='l2h-5006' xml:id='l2h-5006'>cmp_op</tt></b></dt> |
| 173 | <dd> |
| 174 | Sequence of all compare operation names. |
| 175 | </dd></dl> |
| 176 | |
| 177 | <P> |
| 178 | <dl><dt><b><tt id='l2h-5007' xml:id='l2h-5007'>hasconst</tt></b></dt> |
| 179 | <dd> |
| 180 | Sequence of byte codes that have a constant parameter. |
| 181 | </dd></dl> |
| 182 | |
| 183 | <P> |
| 184 | <dl><dt><b><tt id='l2h-5008' xml:id='l2h-5008'>hasfree</tt></b></dt> |
| 185 | <dd> |
| 186 | Sequence of byte codes that access a free variable. |
| 187 | </dd></dl> |
| 188 | |
| 189 | <P> |
| 190 | <dl><dt><b><tt id='l2h-5009' xml:id='l2h-5009'>hasname</tt></b></dt> |
| 191 | <dd> |
| 192 | Sequence of byte codes that access an attribute by name. |
| 193 | </dd></dl> |
| 194 | |
| 195 | <P> |
| 196 | <dl><dt><b><tt id='l2h-5010' xml:id='l2h-5010'>hasjrel</tt></b></dt> |
| 197 | <dd> |
| 198 | Sequence of byte codes that have a relative jump target. |
| 199 | </dd></dl> |
| 200 | |
| 201 | <P> |
| 202 | <dl><dt><b><tt id='l2h-5011' xml:id='l2h-5011'>hasjabs</tt></b></dt> |
| 203 | <dd> |
| 204 | Sequence of byte codes that have an absolute jump target. |
| 205 | </dd></dl> |
| 206 | |
| 207 | <P> |
| 208 | <dl><dt><b><tt id='l2h-5012' xml:id='l2h-5012'>haslocal</tt></b></dt> |
| 209 | <dd> |
| 210 | Sequence of byte codes that access a local variable. |
| 211 | </dd></dl> |
| 212 | |
| 213 | <P> |
| 214 | <dl><dt><b><tt id='l2h-5013' xml:id='l2h-5013'>hascompare</tt></b></dt> |
| 215 | <dd> |
| 216 | Sequence of byte codes of Boolean operations. |
| 217 | </dd></dl> |
| 218 | |
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