any macro-like construct/technique/trick?

Roy Smith roy at panix.com
Sun Jun 5 14:55:12 CEST 2005


"Mac" <idontneednostinkinid at yahoo.com> wrote:
> Is there a way to mimic the behaviour of C/C++'s preprocessor for
> macros?
> [...]
> 
> * using
>    def debug_emit(obj):
>        if debug:
>            emit_dbg_obj(obj)
> is a poor solution, because it *always* instantiates DbgObj*, even when
> not needed; I want to avoid such unnecessary waste

How about using assert statements?  When you run with optimization turned 
on, they don't even get compiled.  Try something like this:

class Debug:
    def __init__ (self, message):
        print "debug (%s)" % message

print "foo"
assert (Debug ("bar"))

which produces:

Roy-Smiths-Computer:play$ python x.py
foo
debug (bar)
Roy-Smiths-Computer:play$ python -O x.py
foo

Notice that the Debug() object doesn't even get created when optimization 
is turned on.  It's a little funky, but at least anybody who knows python 
will understand your code.  I agree with Andrew Dalke when he says of 
preprocessors:

> It's typically a bad idea because you're in essence creating a
> new language that is similar to but not Python, making it harder
> for people to understand what's going on.



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