On Fri, Apr 8, 2016 at 5:06 AM, Terry Reedy <tjreedy@udel.edu> wrote:
On 4/7/2016 11:03 AM, Ethan Furman wrote:
On 04/07/2016 07:07 AM, Random832 wrote:
What's __index__ for?
__index__ is a way to get an int from an int-like object without losing information; so it fails with values like 3.4, but should succeed with values like Fraction(4, 2).
__int__ is a way to convert the value to an int, so 3.4 becomes 3 (and and the 4/10's is lost).
Why is that a problem? Loss is not the issue. And as someone else pointed out, int('4') does not lose information, but seq['1'] is prohibited. Why is passing integer strings as indexes bad?
The answer to the latter, I believe, is that Guido is against treating numbers and string representations of numbers as interchangable. And the answer to both, I believe, is that the downside of flexibility is ease of creating buggy code, especially code where bugs do not immediately raise something, or ease of creating confusing code that is hard to maintain.
Hence my wording of "string-like". Anything can be converted to a string, but only certain objects are sufficiently string-like to be implicitly treated as strings. But ultimately it's all the same concept. ChrisA