Search code examples
pythonmonkeypatching

How to replace a function call in an existing method

given a module with a class Foo with a method that calls a function bar defined in the module scope, is there a way to substitute bar for a different function without modification to the module?

class Foo(object):
    def run(self):
        bar()

def bar():
    return True

I then have a an instance of Foo for which I would like to substitute a function baz() for bar() without having to modify the Foo class.

Solution

  • Let's assume your module is called deadbeef, and you're using it like this

    import deadbeef
…
foo_instance = deadbeef.Foo()

    Then you could do 

    import deadbeef
deadbeef.bar = baz 
…