Python Wrap Class Method

Question

I'm trying to create an object with a run method that will be wrapped by a _wrap_run method. I'd like to be able to call the method and it's wrapper by simply typing instance.run() and I'd like to be able to subclass the object so I can override the run() method and have it still execute the wrapper.

More simply put, I want people to be able to subclass A and override run() but still have calls to the run() method execute the wrapper function.

I'm having some difficulty with the mechanics of this. Does anyone have any suggestions regarding this approach?

class A:

    def run(self):
        print "Run A"
        return True

    def _wrap_run(self):
        print "PRE"
        return_value = self.run()
        print "POST"
        return return_value

    run = property(_wrap_run)


a = A()
a.run()
"""
Should Print: 
PRE
Run A
POST
"""


class B(A):

    def run(self):
        print "Run B"
        return True

b = B()
b.run()
"""
Should Print: 
PRE
Run B
POST
"""

Answer 1

What other folks do

class A:
   def do_run( self ):
       """Must be overridden."""
       raise NotImplementedError
   def run( self, *args, **kw ):
       """Must not be overridden.
       You were warned.
       """
       print "PRE"
       return_value = self.do_run(*args, **kw)
       print "POST"
       return return_value

class B(A):
    def do_run(self):
        print "Run B"
        return True

That's usually sufficient.

If you want to worry about someone "breaking" this, stop now. Don't waste time worrying.

It's Python. We're all adults here. All the malicious sociopaths will break all you code by copying it, changing it, and then breaking it. No matter what you do, they'll just copy your code and modify it to break the clever bits.

Everyone else will read your comment and stick by your rules. If they want to use your module/package/framework, they will cooperate.