On Sunday 05 July 2009, Noufal Ibrahim wrote: > Kent Johnson wrote: > [..] > > > Why not just return the value from the function and pass it up > > the call chain? If a call fails return None. Something like this: > > That's what I ended up doing but the first thing occurred to me and > I was just wondering if there's any production code that relies on > the technique.
The Pyparsing library uses exceptions a lot internally. If I understood it right, exceptions are used to tell that a pattern does not match. If the pattern matches the results are transported with a regular 'return'. As it happens quite often that a pattern does not match, exceptions can be considered a regular mechanism for information transport in Pyparsing. There are two types of exceptions in Pyparsing. An exception that means: try the next pattern; and there are exceptions that mean: there was a fatal error, stop parsing. Pyparsing: http://pyparsing.wikispaces.com/ Kind regards, Eike. _______________________________________________ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
