New submission from Mark Dickinson <dicki...@gmail.com>: I just noticed (while responding to issue 8643) that timedelta.total_seconds() has some accuracy problems, especially for negative timedeltas:
Python 3.2a0 (py3k:80840:80842, May 7 2010, 12:29:35) [GCC 4.2.1 (Apple Inc. build 5659)] on darwin Type "help", "copyright", "credits" or "license" for more information. >>> from datetime import timedelta >>> td = timedelta(microseconds = -123) >>> td.total_seconds() # expect -0.000123 -0.0001230000052601099 This could be easily fixed by using integer arithmetic internally instead of float arithmetic: >>> 1e-6 * td.microseconds + td.seconds + 86400 * td.days -0.0001230000052601099 >>> (td.microseconds + 1000000 * (td.seconds + 86400 * td.days)) / 1000000 -0.000123 This works especially nicely in combination with the new float repr and the improved accuracy of true division in 2.7 / 3.2, to give a total_seconds() whose repr is free of noise digits. (Well, for small timedeltas, anyway.) Since total_seconds is new in 2.7 and 3.2, I think it would be good to fix this before the 2.7 release. ---------- components: Extension Modules messages: 105197 nosy: belopolsky, mark.dickinson priority: normal severity: normal stage: needs patch status: open title: timedelta.total_seconds needlessly inaccurate, especially for negative timedeltas type: behavior versions: Python 2.7, Python 3.2 _______________________________________ Python tracker <rep...@bugs.python.org> <http://bugs.python.org/issue8644> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
