decorators only when __debug__ == True

[LX]

On Mar 29, 6:34 pm, MRAB <pyt... at mrabarnett.plus.com> wrote:
> LX wrote:
> > Hi all, I have a question about decorators. I would like to use them
> > for argument checking, and pre/post conditions. However, I don't want
> > the additional overhead when I run in non-debug mode. I could do
> > something like this, using a simple trace example.
>
> > @decorator
> > def pass_decorator(f, *args, **kw): # what about the slow-down that
> > incurs when using pass_decorator?
> >     return f(*args, **kw)
>
> > @decorator
> > def trace_decorator(f, *args, **kw):
> >     print "calling %s with args %s, %s" % (f.func_name, args, kw)
> >     return f(*args, **kw)
>
> > trace_enable_flag = False #__debug__
> > trace = trace_decorator if trace_enable_flag else pass_decorator
>
> > Trouble is, there is still an additional encapsulating function call.
> > Is there any way to eliminate the extra function call altogether?
> > Thanks in advance!
>
> I think you have misunderstood certain details about decorators.
>
> This code with a decorator:
>
>      @decorator
>      def hello():
>          print "hello world"
>
> basically does this:
>
>      def hello():
>          print "hello world"
>      hello = decorator(hello)
>
> so your non-decorator just needs to return the function it was passed:
>
>      def pass_decorator(func):
>          return func
>
> and your trace decorator would be something like this:
>
>      def trace_decorator(func):
>          def show(*args, **kwargs):
>              print "calling %s with args %s, %s" % (func.func_name,
> args, kwargs)
>              result = func(*args, **kwargs)
>              print "returning %s from %s" % (result, func.func_name)
>              return result
>          return show

Sure, but during runtime, pass_decorator will still be called, even
though it doesn't do anything. I am wondering if I can disable this
additional function call at non-debug runtime. In other words, I want
the calling stack to contain no decorator at all, not even
pass_decorator.

I should mention that, in my code, the symbol "decorator" is imported
from Michele Simionato's decorator.py file.