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README.md

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Bytecode Tools

Bytecode tools are combination of multiple necessary modules to play with Python bytecode. Most of the bytecode related modules are version specific and they won't support other python versions.

Bytecode won't be same across versions, new opcodes will be added or opcodes will be removed or modified, so python standard library modules won't work with other version generated bytecodes.

Let's say marshal module, it's purpose is to serialize or deserialize code objects, they are version specific. Like wise dis module, there is a heavy difference in disassembling bytecode to wordcode AND opcode differences make this version incompatible.

Our goal is to make bytecode_tools work with any Cpython version, Aim is to build below tools.

Tool Purpose
unmarshal deserialize the code obejcts.
pydis Disassembler for any Cpython version.
pycdecode Decoder for bytecode chache files (pyc files)
hackdis Hack the disassembled bytecode
decompiler A decompiler for Cpython x.x

How to deal with bytecode_tools?

Install

  1. Clone this repo and python setup.py install or use pip install .

  2. Install directly from PyPi pip install bytecode-tools

Usage

pydis

What is pydis?

pydis is a python disassembler, it can be a drop in replacement for cpython's Lib/dis.py.

Pydis supports all the cpython versions above 2.5, every verion above 2.5 supports other versions. This means, pydis decodes 2.6 bytes code in 3.6 and vice versa.

Why pydis?

Python's dis moduel is super helpful for looking inside code objects, but it won't support other python versions. If the code object is created through python 3.5 and try to disassemble with python3.6, it won't work.

Each python version gets changes to opcodes, there will be ne ones added and few are deleted. Unless you recreate the code object with new python version, the same code object can't be interpreted with old versions.

Disassemble a statement.

>>> from bytecode_tools import pydis
>>> pydis.dis("a=1")
1           0 LOAD_CONST               0 (1)
            2 STORE_NAME               0 (a)
            4 LOAD_CONST               1 (None)
            6 RETURN_VALUE

Disassble a function object.

>>> def foo():
      print(123)
      a = 1
      b = 2
      c = a + b
      return c

>>> pydis.dis(foo)
  2           0 LOAD_GLOBAL              0 (print)
              2 LOAD_CONST               1 (123)
              4 CALL_FUNCTION            1
              6 POP_TOP

  3           8 LOAD_CONST               2 (1)
             10 STORE_FAST               0 (a)

  4          12 LOAD_CONST               3 (2)
             14 STORE_FAST               1 (b)

  5          16 LOAD_FAST                0 (a)
             18 LOAD_FAST                1 (b)
             20 BINARY_ADD
             22 STORE_FAST               2 (c)

  6          24 LOAD_FAST                2 (c)
             26 RETURN_VALUE
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