New submission from Miksus <koli.mik...@gmail.com>:
I am trying to measure time twice and the second measurement gives a time that is 1 microsecond before the first measurement about half of the time. My experiment in short: --------------------------------------------------- import time, datetime start = time.time() end = datetime.datetime.now() start = datetime.datetime.fromtimestamp(start, None) assert end >= start # fails about half the time. --------------------------------------------------- The problem is somewhat interesting. This does not fail: --------------------------------------------------- import time, datetime start = time.time() end = time.time() start = datetime.datetime.fromtimestamp(start, None) end = datetime.datetime.fromtimestamp(end, None) assert end >= start --------------------------------------------------- And neither does this: --------------------------------------------------- import datetime start = datetime.datetime.now() end = datetime.datetime.now() assert end >= start --------------------------------------------------- And it seems datetime.datetime.now() works the same way as to how I handled the "start" time in my first experiment: https://github.com/python/cpython/blob/3.6/Lib/datetime.py#L1514 and therefore the issue seems to be under the hood. I have tested this on two Windows 10 machines (Python 3.6 & 3.8) in which cases this occurred. This did not happen on Raspberry Pi OS using Python 3.7. In short: - The time module imported in datetime.datetime.now() seems to measure time slightly differently than the time module imported by a Python user. - This seems to be Windows specific. My actual application has some code in between the measurements suffering from the same problem thus this is not an issue affecting only toy examples. ---------- components: Library (Lib), Windows messages: 398919 nosy: Miksus, paul.moore, steve.dower, tim.golden, zach.ware priority: normal severity: normal status: open title: Inconsistency between datetime.now() and datetime.fromtimestamp(time.time(), None) versions: Python 3.6, Python 3.8 _______________________________________ Python tracker <rep...@bugs.python.org> <https://bugs.python.org/issue44831> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
