[Python-3000] Making strings non-iterable

[Ian Bicking]

Guido van Rossum wrote:
> On 4/17/06, Ian Bicking <ianb at colorstudy.com> wrote:
> 
>>The proposal wasn't to remove iterability in general, only to require
>>the use of an explicit method when iterating over strings.  It's not a
>>huge change by any means; a speed bump for a small number of people,
>>perhaps, but no real functionality would be removed.  Backward
>>compatibility is also certainly a concern -- and what seems to have
>>soured Guido on the idea as much as anything -- but that doesn't seem to
>>be what has you bothered.
> 
> 
> "A speed bump for a small number of people"? "No real functionality
> remove"? You gotta be kidding. It drops polymorphism between strings
> and other sequences. This is not just of theoretical value -- difflib
> relies on this, for example. Your (earlier) assertion that the stdlib
> is atypical is wishful thinking; the stdlib contains lots of code just
> like code written by regular people. Perhaps you've had Perl on your
> mind too much recently?

Polymorphism between things that aren't similar is bad; in another 
context it is called implicit coersion, like '1'+2=='12'.  That's what 
string iteration looks like to me -- strings aren't sequences of 
strings.  It can be convenient to treat them like sequences, but lots of 
things can be convenient, including '1'+2=='12'.

But I can accept and understand that the change introduces too many 
backward compatibility problems, especially subtle ones like removing 
type equivalencies, which can be very hard to detect or resolve.

-- 
Ian Bicking  /  ianb at colorstudy.com  /  http://blog.ianbicking.org