New submission from Mike Williamson: Ran a test that I expected to pass. When the test failed, I was struck by the strange (incorrect) assertion claim when using unittest.assertAlmostEqual:
AssertionError: 32.78 != 32.775 within 2 places Uhmm... yes it does! I delved in, discovering that assertAlmostEquals simply calls round. So, I tried it with round, shown below: >>> round(32.775, 2) 32.77 >>> round(32.785, 2) 32.78 >>> round(32.745, 2) 32.74 >>> round(32.746, 2) 32.75 I then looked at the documentation, to understand whether this odd behavior is indeed expected. I saw (on https://docs.python.org/3/library/functions.html#round ): --- If two multiples are equally close, rounding is done toward the even choice (so, for example, both round(0.5) and round(-0.5) are 0, and round(1.5) is 2). --- However, as you can see, this is not the behavior I'm experiencing. So, it looks like a real bug. I am attaching the two files where I was running the unit tests, but I'm not sure you really need them. Thank you! ---------- components: Library (Lib) files: bad_tests.py messages: 279456 nosy: lazarillo priority: normal severity: normal status: open title: round seems to provide floor, not proper rounding type: behavior versions: Python 3.5 Added file: http://bugs.python.org/file45224/bad_tests.py _______________________________________ Python tracker <rep...@bugs.python.org> <http://bugs.python.org/issue28535> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
