Comments on: Using exception or assertation

By: Bas Westerbaan

Bas Westerbaan — Fri, 04 Mar 2005 16:12:13 +0000

Assertations are used in debugging for they only should be called when there is some programatical error in the architecture while programming (programmer’s fault, not system or user’s or environment’s). But this doens’t limit them to debugging. In some cases where a programmer finds a certain assertation so important that he keeps it there.

By: Noud

Noud — Fri, 04 Mar 2005 07:35:44 +0000

To be quite more exact. Assert ought to be used for debugging, assert values should be right, if they aren’t the program contains a bug and will fail. When finalise the program there should be no assert in the code. I thought.

By: Bas Westerbaan

Bas Westerbaan — Tue, 01 Mar 2005 14:19:36 +0000

Python allows the use of exceptions as they are meant to be used.
In most other languages exceptions are *very* slow and therefore there are usualy test functions which have to be used instead of catching exceptions which I think is a shame.

For instance Int.Parse in .net throws an exception when it can’t be parsed.. throwing exceptions takes time.
Int.TryParse doesn’t throw an exception when parsing fails but just returns false, so that one has to be used whether you like it or not.

By: Gumuz

Gumuz — Mon, 28 Feb 2005 23:00:17 +0000

Well said. Python lives by this ‘exception =! error’ rule. It’s a common idiom called (i think): ‘ask forgiveness instead of permission’ as in:

try:
i = list[2]
except IndexError:
i = 0

if the list doesnt contain the required item, it uses a default. no harm done.