如何将不带时区的datetime字符串转换为python中带时区的另一个datetime？

Question

I can't seem to figure out how to convert a datetime string to another datetime string with timezone.

Here's the example.

07/27/2015:06:00 AM to 20150727060000 -0400

The default timezone would be EST.

Here's my code so far.

from datetime import datetime, timedelta
def _to_datetime(air_date, air_time):
    schedule_time = '{}:{}'.format(air_date, air_time)
    return datetime.strptime(schedule_time,'%m/%d/%Y:%I:%M %p')

Answer 1

Use pytz module to work with timezones in Python. To get the local timezone as pytz tzinfo object, you could use tzlocal module:

from tzlocal import get_localzone # $ pip install tzlocal

naive = _to_datetime('07/27/2015', '06:00 AM')
aware = get_localzone().localize(naive, is_dst=None)
print(aware.strftime('%Y%m%d%H%M%S %z'))
# -> 20150727060000 -0400

Answer 2

Add the time zone to the parsed string with %z . This will give it a tzinfo attribute:

from datetime import datetime, timedelta
def _to_datetime(air_date, air_time):
    schedule_time = '{}:{}'.format(air_date, air_time)
    return datetime.strptime(schedule_time + ' -0400', '%m/%d/%Y:%I:%M %p %z')

Example:

>>> datetime.strptime('03/19/2015:03:00 PM -0400','%m/%d/%Y:%I:%M %p %z')
datetime.datetime(2015, 3, 19, 15, 0, tzinfo=datetime.timezone(datetime.timedelta(-1, 72000)))

Answer 3

You could use dateutil to add the tzinfo to the datetime object.

from datetime import datetime, timedelta
from dateutil import tz

AmericaNewYorkTz = tz.gettz('America/New_York')

def _to_datetime(air_date, air_time):
    schedule_time = '{}:{}'.format(air_date, air_time)
    return datetime.strptime(schedule_time,'%m/%d/%Y:%I:%M %p').replace(tzinfo=AmericaNewYorkTz)

dt = _to_datetime('07/27/2015', '06:00 AM')
print('DateTime:', dt)
# DateTime: 2015-07-27 06:00:00-04:00

or as JH Sebastian pointed out, you can use pytz

from datetime import datetime, timedelta
from pytz import timezone

AmericaNewYorkTz = timezone('America/New_York')

def _to_datetime(air_date, air_time):
    schedule_time = '{}:{}'.format(air_date, air_time)
    naiveDateTime = datetime.strptime(schedule_time,'%m/%d/%Y:%I:%M %p') 
    localizedDateTime = AmericaNewYorkTz.localize(naiveDateTime, is_dst=None)
    return localizedDateTime

dt = _to_datetime('05/27/2015', '06:00 AM')
print('DateTime:', dt)