Monkey Patching

This was mentioned in passing in a python book I read and I ignored it until I saw it being used to discover the internals of frozen/obfuscated python code.

It is a great term, basically you can overload defined functions with your own code, this is particularly useful for code testing. For example I have seen someone discuss testing an emailing function and rather than send out lots of emails they monkey patch parts of smtplib to add the messages to a dictionary.

A simple example
class orig:
    def method1(self):
         print "Original method1()"

    def method2(self):
        print "Original method2()"

if __name__ == "__main__":

    obj = orig()

    def monkeypatch():
        print "Monkey code!"

    print "method1()"
    obj.method1()
    obj.method1 = monkeypatch
    print "method1()"
    obj.method1()
    print "method2()"
    obj.method2()