Monkey-patch Python class

Question

I've got a class, located in a separate module, which I can't change.

from module import MyClass  class ReplaceClass(object)   ...  MyClass = ReplaceClass 

This doesn't change MyClass anywhere else but this file. However if I'll add a method like this

def bar():    print 123  MyClass.foo = bar 

this will work and foo method will be available everywhere else.

How do I replace the class completely?

Answer 1

import module class ReplaceClass(object):     .... module.MyClass = ReplaceClass 

Answer 2

Avoid the from ... import (horrid;-) way to get barenames when what you need most often are qualified names. Once you do things the right Pythonic way:

import module  class ReplaceClass(object): ...  module.MyClass = ReplaceClass 

This way, you're monkeypatching the module object, which is what you need and will work when that module is used for others. With the from ... form, you just don't have the module object (one way to look at the glaring defect of most people's use of from ...) and so you're obviously worse off;-);

The one way in which I recommend using the from statement is to import a module from within a package:

from some.package.here import amodule 

so you're still getting the module object and will use qualified names for all the names in that module.