Steven D'Aprano wrote: > On Mon, 21 Dec 2009 21:49:11 +0000, r0g wrote: > >> I use assertions myself e.g. >> >>>>> foo = "123456" >>>>> assert len(foo) <= 5 >> Traceback (most recent call last): >> File "<stdin>", line 1, in <module> >> AssertionError >> >> >> Dunno if this would be considered good or bad programming practice by >> those more experienced than I (comment always welcome!) but it works for >> me :) > > > Bad practice. > > Assertions are ignored when you run Python with the -O (optimization) > command line switch. Your code will behave differently if you use > assertions. So you should never use assertions for error-checking, except > perhaps for quick-and-dirty throw-away scripts. > > Assertions are useful for testing invariants and "this will never happen" > conditions. A trivial example: > > result = math.sin(2*math.pi*x) > assert -1 <= result <= 1 > > Assertions are also useful in testing, although be careful: since the > assert statement is ignored when running with -O, that means you can't > test your application when running with -O either! But do not use them > for data validation unless you're happy to run your application with no > validation at all. > > >
Yikes, glad to be set me straight on that one! Thanks :) It's a pity though, I really like the way it reads. Is there anything similar with ISN'T disabled when optimizations are turned on? I guess I could do the following but it seems a bit ugly in comparison :( if len(foo) <= 5: raise Exception Roger. -- http://mail.python.org/mailman/listinfo/python-list
