runtimeBuiltinAttributeInjection.py

import ctypes as c

class PyObject_HEAD(c.Structure):
    _fields_ = [
        ('HEAD', c.c_ubyte * (object.__basicsize__ - c.sizeof(c.c_void_p))),
        ('ob_type', c.c_void_p)
    ]

_get_dict = c.pythonapi._PyObject_GetDictPtr
_get_dict.restype = c.POINTER(c.py_object)
_get_dict.argtypes = [c.py_object]

customTypes = {
  'appendDougnuts': lambda self, number: self + ('o' * number),
  'oddOrEven': lambda self: '"' + self + '" is: ' + ('Even' if len(self) % 2 == 0 else 'Odd')
}; _get_dict(str).contents.value = {**_get_dict(str).contents.value, **customTypes}

print ('Hello'.appendDougnuts(33))
#--> Helloooooooooooooooooooooooooooooooooo

print ('Helloo'.oddOrEven())
#--> "Helloo" is: Even