Strings are iterable, but not Iterable?

[imjasonh]

Docs for String says:

A String is an immutable sequence of bytes. Strings are iterable; iteration over a string yields each of its 1-byte substrings in order.

But String doesn't implement Iterable's Iterate method.

Is this intentional?

String could implement Iterable, in theory, by returning an iterator which passes each one-byte substring into Next.

[alandonovan]

The doc comment is out of date. The spec was changed relatively recently to makes strings not-iterable, because more often than not, iterating over a string is a mistake. (The usual symptom is that one means to iterate over the list ["foo"] but instead iterates over "foo", yielding the values "f", "o", "o". Because the elements of the iteration have the same type as the sequence as a whole, often the mistake goes unnoticed. The two staff at Google with single-letter userids receive a lot of unintended e-mail sent by errant Python programs.)

Instead of string being iterable, four methods were added to string that return iterable values. This approach also makes the intention more obvious as to whether you're iterating over string elements (bytes) or Unicode code points, and whether numeric values or substrings are desired.

[imjasonh]

Great, I was hoping this wouldn't go down the path Python chose, and was nervous when I read the doc string. :)

[alandonovan]

Re-opening as a documentation issue.