What is proper way to require a method to be overridden?

[Carl Banks]

Well...

How about not defining it on the base class, but check in the
constructor that the attribute exists and that it is of type
FunctionType ?

That still delays the check until the object is created.

You'd have to use metaclass programming to check this during class
creation time.


Carl Banks

 

[sjdevnull]

Decorators to the rescue?

def must_override(f):
def t(*args):
raise NotImplementedError("You must override " + f.__name__)
return t

class Foo:
@must_override
def Bar(x,y): pass

Foo().Bar()

Traceback (most recent call last):
File "testit.py", line 14, in ?
Foo().Bar()
File "testit.py", line 5, in t
raise NotImplementedError("You must override " + f.__name__)
NotImplementedError: You must override Bar

I'd think twice before using a decorator. This just seems less clear
to read than simply raising NotImplementedError, and the traceback
points into the decorator instead of the function that you really care
about.

 

[Bruno Desthuilliers]

Patrick Down a écrit :

(snip)

Decorators to the rescue?

(snip convoluted code)

What a strange idea...