Re: [Python-Dev] Why are so many built-in types inheritable?

[Alex Martelli]

On Mar 13, 2006, at 12:29 PM, Fabiano Sidler wrote:

> Hi folks!

Hello Fabiano!  The proper venue for your interesting issues is  
comp.lang.python (or the equivalent mailing list), where all sorts of  
people will be able to "hear" you, discuss things, and help out.   
python-dev is strictly for developers of Python itself, so please re- 
post your issues to comp.lang.python.


Thanks,

Alex


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[Python-Dev] Why are so many built-in types inheritable?

[Fabiano Sidler]

Hi folks!

Let me explain the above question:
For debugging purpose I tried this:

--- snip ---
def foo(): pass
function = type(foo)

class PrintingFunction(function):
  def __init__(self, func):
self.func = func
  def __call__(self, *args, **kwargs):
print args, kwargs
return function.__call__(self, args, kwargs)

class DebugMeta(type):
  def __new__(self, name, bases, dict):
for name in dict:
  if type(dict[name]) is function:
dict[name] = PrintingFunction(dict[name])

--- snap ---

Now I tought I were able to let all methods of classes with DebugMeta
as metaclass print out their arguments.  But I got the following sad
error:

TypeError: Error when calling the metaclass bases
type 'function' is not an acceptable base type

That's a pity, isn't it?
What could I do to get the above code to work? (No, I don't want to
reimplement  without this unpleasant behaviour in
Python.

Greetings,
F. Sidler
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