On Thu, 23 Jul 2020 at 16:25, Stephen J. Turnbull < email@example.com> wrote:
Mathew Elman writes:
Frankly, saying that a part of a language that is frequently misunderstood, is *never* allowed to be improved is disappointing when the suggestion that it can be (somehow) has been so well received by everyone else.
The highly improbable is frequently well-received.
What can surely be improved is the documentation, specifically the Tutorial. Something like
The else clause of a loop statement has frequently been misunderstood. In a for or while loop *statement*, on each iteration, the condition is tested and exactly one of the following occurs: 1. If truthy, the loop *suite* runs to completion and the test is repeated for the next iteration, 2. OR the loop *suite* runs and there is a nonlocal exit such as return or break or raise, which exits the statement as well. 3. OTHERWISE the condition is false, and the else suite, if any, runs, then the statement is exited.
The emphasis is for contrast in this discussion. The Language Reference already says precisely this, although much more concisely.
I don't expect supporters of "elif not break" etc to think this is sufficient, and supporters of the Else Ban similarly. Please consider if this is helps clarify the Tutorial, and if it doesn't get booed into oblivion, I'll work up a patch (I think that the section on control flow would benefit from some reorganization as well, "just stick it in somewhere" is not what I have in mind :-).
Credit where credit is due, I think this is definitely an improvement. It does make it require slightly less meticulous reading to understand `else`. However, I still think that there is value in improving the `for...else` and `while...else` intuitiveness, if it can be done at an acceptable cost. (As is the case with any change)
IMO the solution is not to change `else` but to add an additional with the opposite meaning that makes the use of `else` with `for` and `while` more intuitive, such as adding `elif`, which feels natural, and a special boolean, which perhaps doesn't. Or adding `except` for catching raised Exceptions rather than breaks, which makes `else` clearly behave how it does for `try`. Or another solution that achieves the additional clarity *without* removing/changing else itself.