Irit Katriel <iritkatr...@yahoo.com> added the comment:
This issue only impacts container objects where the len(repr(o)) is less than width. If the length is greater than width, containers are handled by a different code path which is covered by a unit test and works correctly. For this case, indeed it works in Python 2 but not in Python 3. The PrettyPrinter._format code has been refactored quite a lot with respect to handling of containers. In both Python 2 and 3 this happens: PrettyPrinter.pprint([10]) calls PrettyPrinter._format([10]) which calls PrettyPrinter._repr([10]) which calls MyPrettyPrinter.format([10]) which calls PrettyPrinter.format([10]) which calls _safe_repr([10]) which calls _safe_repr(10) returns 10 returns [10] returns [10] returns [10] returns [10] But then they diverge - in Python 3 the [10] is returned as the result, but in Python 2 there is another piece of code (starting here https://github.com/python/cpython/blob/fdda200195f9747e411d3491aae0806bc1fcd919/Lib/pprint.py#L179) which overrides this result and recalculates the representation for containers. In our case it does: since issubclass(type([10]), list): # ignore the [10] calculated above, now call self._format(10) which calls PrettyPrinter._repr(10) which calls MyPrettyPrinter.format(10) returns 0xa returns 0xa returns 0xa returns [0xa] This explains the difference between Python 2 and 3. As to why the first calculation returns [10] and not [0xa]: This is because _safe_repr is defined at module scope, so once it is called we are no longer on the PrettyPrinter instance, and the format() override is no longer accessible. When _safe_repr needs to recurse on container contents, it calls itself. I think the solution is to make _safe_repr a method of PrettyPrinter, and make it call self.format() when it needs to recurse. The default self.format() just calls _safe_repr, so when there is no override the result is the same. The PR's diff looks substantial, but that's mostly due to the indentation of _safe_repr code. To make it easier to review, I split it into several commits, where the indentation is done in one commit as a noop change. The other commits have much smaller diffs. ---------- versions: +Python 3.10, Python 3.8, Python 3.9 -Python 3.5, Python 3.6, Python 3.7 _______________________________________ Python tracker <rep...@bugs.python.org> <https://bugs.python.org/issue28850> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com