Metaclass Recipe: Automatic Debugger Methods
============================================

Step 2
------
In this step, we will modify the ``get_debugger_func`` decorator to invoke the interactive debugger after printing the exception traceback.

Your task, once again, is to implement the ``__debugger__`` metaclass.

.. sourcecode:: python

    import inspect, traceback, sys, pdb

    def get_debugger_func(func):
        def new_func(*args):
            try:
                return func(*args)
            except Exception,e:
                traceback.print_exc()
                print '-'*80
                pdb.post_mortem(sys.exc_traceback)

        return new_func

    class __debugger__(type):
        """Define this class"""
            
    class Example(object):
        __metaclass__ = __debugger__

        def divide(self, v):
            # exception if v == 0
            result = 100 / v     
            return result

        def interpolate(self, *args):
            # exception if len(args) != 2
            result = "%s is %s!" % args  
            return result

    if __name__ == '__main__':
        e = Example()

        print e.divide(0)

        print '-'*80
        
        print e.interpolate('Feihong', 'very', 'cool')

    
Expected output::

    Traceback (most recent call last):
      File "D:\Projects\PyCon 2008 Talks\framework-tutorial\src\metaclass\debugger\solutions\debugger2.py", line 11, in new_func
        return func(*args)
      File "D:\Projects\PyCon 2008 Talks\framework-tutorial\src\metaclass\debugger\solutions\debugger2.py", line 33, in divide
        result = 100 / v
    ZeroDivisionError: integer division or modulo by zero
    --------------------------------------------------------------------------------
    > d:\projects\pycon 2008 talks\framework-tutorial\src\metaclass\debugger\solutions\debugger2.py(33)divide()
    -> result = 100 / v
    (Pdb) c
    None
    --------------------------------------------------------------------------------
    Traceback (most recent call last):
      File "D:\Projects\PyCon 2008 Talks\framework-tutorial\src\metaclass\debugger\solutions\debugger2.py", line 11, in new_func
        return func(*args)
      File "D:\Projects\PyCon 2008 Talks\framework-tutorial\src\metaclass\debugger\solutions\debugger2.py", line 38, in interpolate
        result = "%s is %s!" % args
    TypeError: not all arguments converted during string formatting
    --------------------------------------------------------------------------------
    > d:\projects\pycon 2008 talks\framework-tutorial\src\metaclass\debugger\solutions\debugger2.py(38)interpolate()
    -> result = "%s is %s!" % args
    (Pdb)     

Hints:

.. class:: hintlist

#. The solution to this step is **very similar** to the solution from the last step.
#. Actually, the definition of ``__debugger__`` is completely identical. This was just a trick question to see if you were paying attention.
    
Solution: `debugger2.py <solutions/debugger2.py>`_    

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