Hack a class's __init__ method without subclassing the class because a) you can't modify the original class and b) you can't modify other classes already using the first class. This is a gross hack that should only be used to work around flaws in libraries you have no control over. I've changed the names to protect the innocent.
Python, 36 lines
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Copy to clipboard1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 | """HACK: Make module.ClassWithUnsafeInit safe."""
import module
def enable_safety():
"""HACK: Make ClassWithUnsafeInit safe.
module.ClassWithUnsafeInit does something unsafe.
Move the old ClassWithUnsafeInit.__init__ method out of the way--name it
_NowSafeOrigInit. Move the old ClassWithUnsafeInit class out of the
way--name it _NowSafeClassWithUnsafeInit. Create a new function,
_NowSafeNewClassWithUnsafeInit, in place of the ClassWithUnsafeInit class
that instantiates _NowSafeClassWithUnsafeInit and then calls
_NowSafeClassWithUnsafeInit._NowSafeOrigInit (thanks go to Paul Abrams for
this second part of the hack). Last of all, ClassWithUnsafeInit has a
ClassWithUnsafeInitClass attribute. Set this to
_NowSafeNewClassWithUnsafeInit. I accept the fact that there's probably a
special place in programmer hell for me (and Paul).
This must be called exactly once, and it must be called before
ClassWithUnsafeInit is used for the first time.
"""
ClassWithUnsafeInit._NowSafeOrigInit = ClassWithUnsafeInit.__init__
module._NowSafeClassWithUnsafeInit = ClassWithUnsafeInit
ClassWithUnsafeInit = _NowSafeNewClassWithUnsafeInit
ClassWithUnsafeInitClass = _NowSafeNewClassWithUnsafeInit
def _NowSafeNewClassWithUnsafeInit(*args, **kargs):
fs = module._NowSafeClassWithUnsafeInit()
# Do whatever you need here.
fs._NowSafeOrigInit(*args, **kargs)
return fs
|
This shows you how to replace an __init__ method. The HasFriends recipe shows you how to add (and thus replace) any other type of method.
Tags: oop
