Python time utils

time_utils.py

import datetime
import pytz

# careful, don't assume now() is nyc time! on ec2, it's utc time.
def datetime_from_tz_naive_nyc_to_tz_aware_utc(nyc_datetime_tz_naive):
  nyc_datetime_tz_aware = pytz.timezone('US/Eastern').localize(nyc_datetime_tz_naive)
  return nyc_datetime_tz_aware.astimezone(pytz.utc)

def utc_tz_aware(utc_datetime_tz_naive):
  return pytz.timezone('UTC').localize(utc_datetime_tz_naive)

def utcnow_tz_aware():
  utcnow_tz_naive = datetime.datetime.utcnow()
  return utc_tz_aware(utcnow_tz_naive)


def seconds_until_utc_time(utc_datetime_later):
#  utc_datetime_now = datetime_from_tz_naive_nyc_to_tz_aware_utc(datetime.datetime.now())
  utc_datetime_now = utcnow_tz_aware()
  datetime_diff_timedelta = utc_datetime_later - utc_datetime_now
  # can be negative, if "later" is actually in the past!
  seconds_until_later = datetime_diff_timedelta.days * 86400 + datetime_diff_timedelta.seconds
  return seconds_until_later


def get_utc_datetime_n_secs_in_future(n_secs):
  return (utcnow_tz_aware() + datetime.timedelta(seconds=n_secs))

# ISO format to expect: 2017-08-24T09:47:57.883578-00:00
# drop microseconds and timezone; assume UTC
def strptime_utc_to_tz_aware_utc(utc_datetime_str):
  try:
    utc_datetime_tz_naive = datetime.datetime.strptime(utc_datetime_str[0:19], '%Y-%m-%dT%H:%M:%S')
  except:
    try:
      utc_datetime_tz_naive = datetime.datetime.strptime(utc_datetime_str[0:19], '%Y-%m-%d %H:%M:%S')
    except:
      return None
  return utc_tz_aware(utc_datetime_tz_naive)