30.10 dis -- Disassembler for Python byte code

Python 2.5

previous page next page

30.10 `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

(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: