cascading python executions only if return code is 0

Roy Smith roy at
Sun Dec 22 22:53:31 CET 2013

In article <mailman.4512.1387748397.18130.python-list at>,
 Cameron Simpson <cs at> wrote:

> Roy's code _depends_ upon the return value being equivalent to False.

Yes.  You view this as a flaw.  I view it as a feature :-)

> A better approach would be:
>   a() == 0 and b() == 1 and c() == 0
> i.e. to explicitly check each return code against the expected/desired
> value instead of relying on some flukey coincidental property of
> the (arbitrary) numeric value returned.

You're assuming it's arbitrary.  I'm saying do it that way by design.  

> Better still is the suggestion elsewhere in the thread to make the functions
> raise exceptions on error instead of returning a number.

Possibly.  But, I think of exceptions as indicating that something went 
wrong.  There's two possible things the OP was trying to do here:

1) He intends that all of the functions get run, but each one can only 
get run if all the ones before it succeed.  In that case, I agree that 
the exception pattern makes sense.

2) He intends that each of the functions gets tried, and the first one 
that can return a value wins.  If that's the case, the "or" chaining 
seems more natural.

More information about the Python-list mailing list