[Python-Dev] co_firstlineno on decorated functions

[Antoine Pitrou]

On Tue, 3 Aug 2010 22:25:01 +1000
Nick Coghlan <ncoghlan at gmail.com> wrote:
> On Tue, Aug 3, 2010 at 1:40 PM, Eli Bendersky <eliben at gmail.com> wrote:
> > The first print out correctly specifies the line "def foo" is in. However,
> > the second one points to the line with "@dummydecorator" instead of "def
> > bar". [Python 2.6]
> >
> > The side-effects of this behavior can be easily seen in the output of
> > modules like trace and profile. Would you say it's normal, or could this be
> > considered a bug?
> 
> Since the decorator is as much a part of the function definition as
> the def line is, I would say that it is correct (the name says
> "firstlineno", not "deflineno").

That's debatable. Since writing:

@b
def a():
    ...

is equivalent to:

def a():
    ...
a = b(a)

and in the latter case co_firstlineno points to the "def a()" line.

Furthermore, co_firstlineno is an attribute of the code object, not the
function object, so it shouldn't ideally depend on whether a decorator
was applied or not.

Regards

Antoine.