parse_date_time.py

#! /usr/bin/env python
# vim: et:ts=4:sts=4:sw=4:fileencoding=utf-8
ur"""
Parse a date/time string.

Usage:
    python {script} FORMAT DATE [LOCALE]

Example:

    $ python {script} "%d %B %Y" "15 mai 2017" fr_FR
    time.struct_time(tm_year=2017, tm_mon=5, tm_mday=15, tm_hour=0, tm_min=0, tm_sec=0, tm_wday=0, tm_yday=135, tm_isdst=-1)
    1494820800.0
    2017-05-15 00:00:00-0400

    $ /cygdrive/c/Python27/python {script} "%d %B %Y" "15 mai 2017" French
    time.struct_time(tm_year=2017, tm_mon=5, tm_mday=15, tm_hour=0, tm_min=0, tm_sec=0, tm_wday=0, tm_yday=135, tm_isdst=-1)
    1494820800.0
    2017-05-15 00:00:00-0400

    C:\DIR>\Python27\python {script} "%d %B %Y" "15 mai 2017" French
    time.struct_time(tm_year=2017, tm_mon=5, tm_mday=15, tm_hour=0, tm_min=0, tm_sec=0, tm_wday=0, tm_yday=135, tm_isdst=-1)
    1494820800.0
    2017-05-15 00:00:00-0400
"""


import os
if os.name == "nt":
    # Check if executing the Windows build of Python from a Cygwin shell.
    if "TZ" in os.environ:
        # The Windows build of Python (as opposed to the Cygwin one) appears
        # confused with the TZ variable set by the Cygwin shell.  The former
        # sets time.timezone to 0, time.altzone to -3600 (-1 hr) in the
        # presence of TZ="America/New_York", which turns the local time zone to
        # UTC.
        del os.environ["TZ"]

import time
import locale
import threading
from contextlib import contextmanager


class Usage(SystemExit):
    def __init__(self):
        super(Usage, self).__init__(__doc__.format(script=os.path.basename(__file__)))


# "How do I strftime a date object in a different locale?"
# https://stackoverflow.com/a/24070673/80772 by Daniel, June 5, 2014
LOCALE_LOCK = threading.Lock()


@contextmanager
def setlocale(name):
    with LOCALE_LOCK:
        saved = locale.setlocale(locale.LC_ALL)
        try:
            yield locale.setlocale(locale.LC_ALL, name)
        finally:
            locale.setlocale(locale.LC_ALL, saved)


def local_timestamp(s_since_epoch):
    t = time.localtime(s_since_epoch)
    is_dst = time.daylight and t.tm_isdst
    zone = time.altzone if is_dst else time.timezone
    strtime = time.strftime("%Y-%m-%d %H:%M:%S", t)
    utcoff = -zone
    if utcoff > 0:
        utcsign = "+"
    else:
        utcsign = "-"
        utcoff = -utcoff
    strtime += ("%s%02d%02d" % (utcsign, utcoff // 3600, (utcoff % 3600) // 60))
    return strtime


def parse_date_time(fmt, dt):
    t = time.strptime(dt, fmt)
    print t
    return time.mktime(t)


if __name__ == "__main__":
    import sys
    args = sys.argv[1:]
    if len(args) not in (2, 3):
        raise Usage()
    fmt = args[0]
    dt = args[1]
    if len(args) == 3:
        loc = args[2]
    else:
        loc = ""
    with setlocale(loc):
        s_since_epoch = parse_date_time(fmt, dt)
        print s_since_epoch
        print local_timestamp(s_since_epoch)