How can I get an accurate UTC time with Python?

问题:

I wrote a desktop application and was using datetime.datetime.utcnow() for timestamping, however I've recently noticed that some people using the application get wildly different results than I do when we run the program at the same time. Is there any way to get the UTC time locally without using urllib to fetch it from a website?

回答1:

Python depends on the underlying operating system to provide an accurate time-of-day clock. If it isn't doing that, you don't have much choice other than to bypass the o/s. There's a pure-Python implementation of an NTP client here. A very simple-minded approach:

>>> import ntplib,datetime
>>> x = ntplib.NTPClient()
>>> datetime.datetime.utcfromtimestamp(x.request('europe.pool.ntp.org').tx_time)
datetime.datetime(2009, 10, 21, 7, 1, 54, 716657)

However, it would not be very nice to be continually hitting on other NTP servers out there. A good net citizen would use the ntp client library to keep track of the offset between the o/s system clock and that obtained from the server and only periodically poll to adjust the time.

回答2:

Actually, ntplib computes this offset accounting for round-trip delay. It's available through the "offset" attribute of the NTP response. Therefore the result should not very wildly.