Re: Optimize flag question

[copied to python-list]

Olivier Langlois wrote:
Hi Steve!

Could you outline the code that needs to be in to make the program

work,

so we can assess the errors for ourselves?



There is nothing unfixable. There are some instances where the code is
checking a function return value like:

assert(Somefunc())

which could fix with

res = Somefunc()
assert(res)

So what you are saying is that Somefunc() needs to be executed, presumably because it has side-effects?

Yes, it would be much better to recast it, but ...

Some other functions rely on the AssertionError exception to indicate to
the user that something went wrong instead of using a user defined
exception.


The real problem here is that you appear to be using AssertionError in an inappropriate way. If some caller passes an incorrect argument to your function, raise a ValueError. If you are passed the wrong type of data, raise a TypeError. And so on. Or, as you imply you thought about, raise a user-defined error.

Generally speaking you should reserve assert for circumstances where you expect some invariant condition to be true. Otherwise use an "if" statement and raise some other exception if the condition is True.

regards
Steve
--
Steve Holden +44 150 684 7255 +1 800 494 3119
Holden Web LLC www.holdenweb.com
PyCon TX 2006 www.python.org/pycon/

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