Issue 22778: list's in-place add doesn't return NotImplemented when appropriate (original) (raw)

Issue22778

Created on 2014-10-31 22:07 by ethan.furman, last changed 2022-04-11 14:58 by admin. This issue is now closed.

Messages (3)
msg230396 - (view)	Author: Ethan Furman (ethan.furman) *	Date: 2014-10-31 22:07
--> s = [] --> s += 1 Traceback (most recent call last): File "", line 1, in TypeError: 'int' object is not iterable For comparison, when NotImplemented is appropriately returned the message looks like this: --> s -= 1 Traceback (most recent call last): File "", line 1, in TypeError: unsupported operand type(s) for -=: 'list' and 'int' Which is certainly more helpful than " object is not iterable"
msg230401 - (view)	Author: Raymond Hettinger (rhettinger) *	Date: 2014-10-31 22:20
Please don't replicate existing issues. Also, this behavior for lists is long-standing, tested, and designed by Guido. More than a little code relies on this behavior.
msg230408 - (view)	Author: Ethan Furman (ethan.furman) *	Date: 2014-10-31 22:43
My understanding was that if a different patch will be needed, it is not the same issue. Is that not correct? Here's the test: def test_iadd(self): ... self.assertRaises(TypeError, u.__iadd__, None) It would still pass, as returning NotImplemented will still result in a TypeError, just with a friendlier message. If any code is depending on this, it is depending on the error message text, which is explicitly not guaranteed