12. dis — Disassembler for Python bytecode¶

The dis module supports the analysis of CPython bytecode by disassembling it. The CPython bytecode 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.dis([bytesource])[source]¶

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 bytecode instruction. If no object is provided, it disassembles the last traceback.

dis.distb([tb])[source]¶

Disassembles the top-of-stack function of a traceback, using the last traceback if none was passed. The instruction causing the exception is indicated.

dis.disassemble(code[, lasti])[source]¶

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.

dis.disco(code[, lasti])¶

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

dis.findlinestarts(code)[source]¶

This generator function uses the co_firstlineno and co_lnotab attributes of the code object code to find the offsets which are starts of lines in the source code. They are generated as (offset, lineno) pairs.

dis.findlabels(code)[source]¶

Detect all offsets in the code object code which are jump targets, and return a list of these offsets.

dis.opname¶

Sequence of operation names, indexable using the bytecode.

dis.opmap¶

Dictionary mapping operation names to bytecodes.

dis.cmp_op¶

Sequence of all compare operation names.

dis.hasconst¶

Sequence of bytecodes that have a constant parameter.

dis.hasfree¶

Sequence of bytecodes that access a free variable.

dis.hasname¶

Sequence of bytecodes that access an attribute by name.

dis.hasjrel¶

Sequence of bytecodes that have a relative jump target.

dis.hasjabs¶

Sequence of bytecodes that have an absolute jump target.

dis.haslocal¶

Sequence of bytecodes that access a local variable.

dis.hascompare¶

Sequence of bytecodes of Boolean operations.