How to pop the interpreter's stack?

[Steven D'Aprano]

On Sun, 26 Dec 2010 09:15:32 -0800, Ethan Furman wrote:

> Steven D'Aprano wrote:
>> Right. But I have thought of a clever trick to get the result KJ was
>> asking for, with the minimum of boilerplate code. Instead of this:
>> 
>> 
>> def _pre_spam(args):
>>     if condition(args):
>>         raise SomeException("message")
>>     if another_condition(args):
>>         raise AnotherException("message")
>>     if third_condition(args):
>>         raise ThirdException("message")
>> 
>> def spam(args):
>>     _pre_spam(args)
>>     do_useful_work()
>> 
>> 
>> you can return the exceptions instead of raising them (exceptions are
>> just objects, like everything else!), and then add one small piece of
>> boilerplate to the spam() function:
>> 
>> 
>> def _pre_spam(args):
>>     if condition(args):
>>         return SomeException("message")
>>     if another_condition(args):
>>         return AnotherException("message")
>>     if third_condition(args):
>>         return ThirdException("message")
>> 
>> def spam(args):
>>     exc = _pre_spam(args)
>>     if exc: raise exc
>>     do_useful_work()
> 
> -1
> 
> You failed to mention that cleverness is not a prime requisite of the
> python programmer -- in fact, it's usually frowned upon.  The big
> problem with the above code is you are back to passing errors in-band,
> pretty much completely defeating the point of have an out-of-band
> channel.

How is that any worse than making _pre_spam() a validation function that 
returns a bool?

def spam(args):
    flag = _pre_spam(args)
    if flag: raise SomeException()
    do_useful_work()


Is that also frowned upon for being too clever?



-- 
Steven