Short-circuit Logic

[Chris Angelico]

On Thu, May 30, 2013 at 10:40 PM, Roy Smith <roy at panix.com> wrote:
> if somebody were to accidentally drop three zeros into the source code:
>
>> x = 1000
>> while x < 173:
>>     print(x)
>>     x += 1
>
> should the loop just quietly not execute (which is what it will do
> here)?  Will that make your program correct again, or will it simply
> turn this into a difficult to find bug?  If you're really worried about
> that, why not:

If you iterate from 1000 to 173, you get nowhere. This is the expected
behaviour; this is what a C-style for loop would be written as, it's
what range() does, it's the normal thing. Going from a particular
starting point to a particular ending point that's earlier than the
start results in no iterations. The alternative would be an infinite
number of iterations, which is far far worse.

ChrisA