Python 将时间戳转换为 unix

Question

I know these questions have been asked before but I'm struggling to convert a timestamp string to a unix time and figuring out whether the datetime objects are naive or aware

For example, to convert the time "2021-05-19 12:51:47" to unix:

>>> from datetime import datetime as dt
>>> dt_obj = dt.strptime("2021-05-19 12:51:47", "%Y-%m-%d %H:%M:%S")
>>> dt_obj
datetime.datetime(2021, 5, 19, 12, 51, 47)

is dt_obj naive or aware and how would you determine this? The methods on dt_obj such as timetz , tzinfo , and tzname don't seem to indicate anything - does that mean that dt_obj is naive?

Then to get unix:

>>> dt_obj.timestamp()
1621421507.0

However when I check 1621421507.0 on say https://www.unixtimestamp.com then it tells me that gmt for the above is Wed May 19 2021 10:51:47 GMT+0000, ie 2 hours behind the original timestamp?

Answer 1

since Python's datetime treats naive datetime as local time by default, you need to set the time zone ( tzinfo attribute):

from datetime import datetime, timezone

# assuming "2021-05-19 12:51:47" represents UTC:
dt_obj = datetime.fromisoformat("2021-05-19 12:51:47").replace(tzinfo=timezone.utc)

Or, as @Wolf suggested, instead of setting the tzinfo attribute explicitly, you can also modify the input string by adding "+00:00" which is parsed to UTC;

dt_obj = datetime.fromisoformat("2021-05-19 12:51:47" + "+00:00")

In any case, the result

dt_obj.timestamp()
# 1621428707.0

now converts as expected on https://www.unixtimestamp.com/ :

Answer 2

As long as you don't specify the timezone when calling strptime , you will produce naive datetime objects. You may pass time zone information via %z format specifier and +00:00 added to the textual date-time representation to get a timezone aware datetime object:

from datetime import datetime

dt_str = "2021-05-19 12:51:47"
print(dt_str)
dt_obj = datetime.strptime(dt_str+"+00:00", "%Y-%m-%d %H:%M:%S%z")
print(dt_obj)
print(dt_obj.timestamp())

The of above script is this:

2021-05-19 12:51:47
2021-05-19 12:51:47+00:00
1621428707.0

Answer 3

datetime.timestamp()

Naive datetime instances are assumed to represent local time and this method relies on the platform C mktime() function to perform the conversion.

So using this does automatically apply yours machine current timezone, following recipe is given to calculate timestamp from naive datetime without influence of timezone:

timestamp = (dt - datetime(1970, 1, 1)) / timedelta(seconds=1)