[Python-iterators] Re: PEP 234: Iterators

[Just van Rossum]

Thomas Bellman wrote:
> 
> Just van Rossum <just at letterror.com> wrote:
> 
> > I think it will be rare for iterators created "manually" with iter(obj) to
> > be passed "manually" to a for loop.
> 
> And just to contradict you, my very first use of Python iterators
> did exactly that.  Of course, my iterator had special methods
> set_start() and set_end() in order to make it start at a certain
> position in the sequence and end at another.
> 
> My program was to download a set of web pages, indexed by a date
> in the URL.  The next() method in the iterator generated the URL
> for the next day, and I didn't want it to start trying to download
> 2000 years worth of web pages...  Thus I would do:
> 
>     ui = iter(obj)
>     ui.set_start(2000,4,23)
>     ui.set_end(2000,5,29)
>     for url in ui:
>         urlopen.urlretrieve(url)
> 
> to download the pages pertaining to dates between April 23rd and
> May 29th, inclusive, last year.  (Actually, it is a bit more
> complicated than that, but at least that is the gist of it.)

Good show! Very nice example: I couldn't dream up a good alternative
spelling that doesn't prove me wrong ;-)

Just