cli.py

#!/usr/bin/env python3

import datetime
import argparse
import re

DT_NOW = datetime.datetime.now()

def mkdate(datestring):
    if isinstance(datestring, datetime.datetime):
        return datestring
    try:
        return datetime.datetime.strptime(datestring, '%Y-%m-%dT%H:%M')
    except ValueError:
        return datetime.datetime.strptime(datestring, '%Y-%m-%d')

# https://gist.github.com/jnothman/4057689
_units = dict(W=7*60*60*24, w=7*60*60*24,
              D=60*60*24, d=60*60*24,
              H=60*60, h=60*60,
              M=60, m=60,
              S=1, s=1)
def mkdelta(deltavalue):
    seconds = 0
    defaultunit = unit = _units['d']  # default to days
    value = ''
    for ch in list(str(deltavalue).strip()):
        if ch.isdigit():
            value += ch
            continue
        if ch in _units:
            unit = _units[ch]
            if value:
                seconds += unit * int(value)
                value = ''
                unit = defaultunit
            continue
        if ch in ' \t':
            # skip whitespace
            continue
        raise ValueError('Invalid time delta: %s' % deltavalue)
    if value:
        seconds = unit * int(value)
    return datetime.timedelta(seconds=seconds)


parser = argparse.ArgumentParser()
parser.add_argument('--start',
                    type=mkdate,
                    help="start date(time) - ISO format e.g. 2016-11-23 or 2016-12-24T14:50")
parser.add_argument('--end',
                    type=mkdate,
                    help="end date(time) - ISO format e.g. 2016-11-23 or 2016-12-24T14:50")
parser.add_argument('--delta',
                    type=mkdelta,
                    help="delta (time delta) - e.g. 1w5d6h7m8s")

args = parser.parse_args()

if args.delta:
    if args.start and args.end:  # all three options set
        raise Exception("too many arguments provided - specfiy either:\n"
                        "1) DELTA (e.g. --days 1) or\n"
                        "2) START (e.g --start 2016-12-24T14:50) or\n"
                        "3) START and END (e.g. --start 2016-01-01 --end 2016-01-31 )")
    elif args.start:  # start and delta set
        raise Exception("invalid argument combination (START and DELTA) - specfiy either:\n"
                        "1) DELTA (e.g. --delta 1w5d) or\n"
                        "2) START (e.g --start 2016-12-24T14:50) or\n"
                        "3) START and END (e.g. --start 2016-01-01 --end 2016-01-31 )")
    else:  # delta and end (use now if end is not set)
        if not args.end:
            dt_end = DT_NOW
        else:
            dt_end = args.end
        dt_start = dt_end - args.delta

else:
    if args.start and args.end:  # start and end given
        dt_start = args.start
        dt_end = args.end
    elif args.start and not args.end:  # start give (use now for end)
        dt_start = args.start
        dt_end = DT_NOW
    else:
        raise Exception("too few arguments provided - specfiy either:\n"
                        "1) DELTA (e.g. --delta 1w5d) or\n"
                        "2) START (e.g --start 2016-12-24T14:50) or\n"
                        "3) START and END (e.g. --start 2016-01-01 --end 2016-01-31 )")

if dt_start > dt_end:
    raise Exception("START has to be an earlier date than END")

print("startT: {}".format(type(dt_start)))
print("start: {}".format(dt_start))

print("endT: {}".format(type(dt_end)))
print("end: {}".format(dt_end))