18.10 dis -- Disassembler for Python byte code

The dis module supports the analysis of Python byte code by disassembling it. Since there is no Python assembler, this module defines the Python assembly language. The Python byte code which this module takes as an input is defined in the file Include/opcode.h and used by the compiler and the interpreter.

Example: Given the function myfunc:

def myfunc(alist):
    return len(alist)

the following command can be used to get the disassembly of myfunc():

>>> dis.dis(myfunc)
  2           0 LOAD_GLOBAL              0 (len)
              3 LOAD_FAST                0 (alist)
              6 CALL_FUNCTION            1
              9 RETURN_VALUE        
             10 LOAD_CONST               0 (None)
             13 RETURN_VALUE

(The ``2'' is a line number).

The dis module defines the following functions and constants:

dis( [bytesource])
Disassemble the bytesource object. bytesource can denote either a module, a class, a method, a function, or a code object. For a module, it disassembles all functions. For a class, it disassembles all methods. For a single code sequence, it prints one line per byte code instruction. If no object is provided, it disassembles the last traceback.

distb( [tb])
Disassembles the top-of-stack function of a traceback, using the last traceback if none was passed. The instruction causing the exception is indicated.

disassemble( code[, lasti])
Disassembles a code object, indicating the last instruction if lasti was provided. The output is divided in the following columns:

  1. the line number, for the first instruction of each line
  2. the current instruction, indicated as "->",
  3. a labelled instruction, indicated with ">>",
  4. the address of the instruction,
  5. the operation code name,
  6. operation parameters, and
  7. interpretation of the parameters in parentheses.

The parameter interpretation recognizes local and global variable names, constant values, branch targets, and compare operators.

disco( code[, lasti])
A synonym for disassemble. It is more convenient to type, and kept for compatibility with earlier Python releases.

opname
Sequence of operation names, indexable using the byte code.

cmp_op
Sequence of all compare operation names.

hasconst
Sequence of byte codes that have a constant parameter.

hasfree
Sequence of byte codes that access a free variable.

hasname
Sequence of byte codes that access an attribute by name.

hasjrel
Sequence of byte codes that have a relative jump target.

hasjabs
Sequence of byte codes that have an absolute jump target.

haslocal
Sequence of byte codes that access a local variable.

hascompare
Sequence of byte codes of Boolean operations.



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