Python UTC datetime object's ISO format doesn&

问题:

Why python 2.7 doesn't include Z character (Zulu or zero offset) at the end of UTC datetime object's isoformat string unlike JavaScript?

>>> datetime.datetime.utcnow().isoformat()
'2013-10-29T09:14:03.895210'

Whereas in javascript

>>>  console.log(new Date().toISOString()); 
2013-10-29T09:38:41.341Z

回答1:

Python datetime objects don't have time zone info by default, and without it, Python actually violates the ISO 8601 specification (if no time zone info is given, assumed to be local time). You can use the pytz package to get some default time zones, or directly subclass tzinfo yourself:

from datetime import datetime, tzinfo, timedelta
class simple_utc(tzinfo):
    def tzname(self,**kwargs):
        return "UTC"
    def utcoffset(self, dt):
        return timedelta(0)

Then you can manually add the time zone info to utcnow():

>>> datetime.utcnow().replace(tzinfo=simple_utc()).isoformat()
'2014-05-16T22:51:53.015001+00:00'

Note that this DOES conform to the ISO 8601 format, which allows for either Z or +00:00 as the suffix for UTC. Note that the latter actually conforms to the standard better, with how time zones are represented in general (UTC is a special case.)

回答2:

Option: isoformat()

Python's datetime does not support the military timezone suffixes like 'Z' suffix for UTC. The following simple string replacement does the trick:

In [1]: import datetime

In [2]: d = datetime.datetime(2014, 12, 10, 12, 0, 0)

In [3]: str(d).replace('+00:00', 'Z')
Out[3]: '2014-12-10 12:00:00Z'

str(d) is essentially the same as d.isoformat(sep=' ')

See: Datetime, Python Standard Library

Option: strftime()

Or you could use strftime to achieve the same effect:

In [4]: d.strftime('%Y-%m-%d %H:%M:%SZ')
Out[4]: '2014-12-10 12:00:00Z'

Note: This option works only when you know the date specified is in UTC.

See: datetime.strftime()

---

Additional: Human Readable Timezone

Going further, you may be interested in displaying human readable timezone information, pytz with strftime %Z timezone flag:

In [5]: import pytz

In [6]: d = datetime.datetime(2014, 12, 10, 12, 0, 0, tzinfo=pytz.utc)

In [7]: d
Out[7]: datetime.datetime(2014, 12, 10, 12, 0, tzinfo=<UTC>)

In [8]: d.strftime('%Y-%m-%d %H:%M:%S %Z')
Out[8]: '2014-12-10 12:00:00 UTC'

回答3:

Python datetimes are a little clunky. Use arrow.

> str(arrow.utcnow())
'2014-05-17T01:18:47.944126+00:00'

Arrow has essentially the same api as datetime, but with timezones and some extra niceties that should be in the main library.

A format compatible with Javascript can be achieved by:

arrow.utcnow().isoformat().replace("+00:00", "Z")
'2018-11-30T02:46:40.714281Z'

Javascript Date.parse will quietly drop microseconds from the timestamp.

回答4:

By combining all answers above I came with following function :

from datetime import datetime, tzinfo, timedelta
class simple_utc(tzinfo):
    def tzname(self,**kwargs):
        return "UTC"
    def utcoffset(self, dt):
        return timedelta(0)


def getdata(yy, mm, dd, h, m, s) :
    d = datetime(yy, mm, dd, h, m, s)
    d = d.replace(tzinfo=simple_utc()).isoformat()
    d = str(d).replace('+00:00', 'Z')
    return d


print getdata(2018, 02, 03, 15, 0, 14)

回答5:

There are a lot of good answers on the post, but I wanted the format to come out exactly as it does with JavaScript. This is what I'm using and it works well.

In [1]: import datetime

In [1]: now = datetime.datetime.utcnow()

In [1]: now.strftime('%Y-%m-%dT%H:%M:%S') + now.strftime('.%f')[:4] + 'Z'
Out[3]: '2018-10-16T13:18:34.856Z'

回答6:

The following javascript and python scripts give identical outputs. I think it's what you are looking for.

JavaScript

new Date().toISOString()

Python

import datetime

datetime.datetime.utcnow().strftime('%Y-%m-%dT%H:%M:%S.%f')[:-3] + 'Z'

The output they give is the utc (zelda) time formatted as an ISO string with a 3 millisecond significant digit and appended with a Z.

2019-01-19T23:20:25.459Z

回答7:

>>> import arrow

>>> now = arrow.utcnow().format('YYYY-MM-DDTHH:mm:ss.SSS')
>>> now
'2018-11-28T21:34:59.235'
>>> zulu = "{}Z".format(now)
>>> zulu
'2018-11-28T21:34:59.235Z'

Or, to get it in one fell swoop:

>>> zulu = "{}Z".format(arrow.utcnow().format('YYYY-MM-DDTHH:mm:ss.SSS'))
>>> zulu
'2018-11-28T21:54:49.639Z'