fishhook

Fishhook

This module allows for swapping out the slot pointers contained in static classes with the generic slot pointers used by python for heap classes. This allows for assigning arbitrary python functions to static class dunders using hook and hook_cls and for applying new functionality to previously unused dunders. A hooked static dunder can be restored to original functionality using the unhook function

it is possible to hook descriptors using hook.property, and an example can be seen below

Calling original methods

orig(self, *args, **kwargs) is a special function that looks up the original implementation of a hooked dunder in the methods cache. It will only work properly when used inside a hooked method where an original implementation existed

hooking single methods

@hook(int)
def __add__(self, other):
  ...
  return orig(self, other)

hooking multiple methods

@hook.cls(int)
class int_hook:
  attr = ...

  def __add__(self, other):
    ...

hooking descriptors

@hook.property(int)
def imag(self):
  ...
  return orig.imag

fishhook.asm

This submodule allows for more in-depth C level hooks. For obvious reasons, this is vastly unstable, mostly provided as an experiment. Originally created as a way to grab a reference to the Interned strings dictionary.

from fishhook import asm
from ctypes import py_object, pythonapi

@asm.hook(pythonapi.PyDict_SetDefault, restype=py_object, argtypes=[py_object, py_object, py_object])
def setdefault(self, key, value):
    if key == 'MAGICVAL':
        return self
    return pythonapi.PyDict_SetDefault(self, key, value)

pythonapi.PyUnicode_InternFromString.restype = py_object
interned = pythonapi.PyUnicode_InternFromString(b'MAGICVAL')

Links

Github

PyPi