Python argparse : mutually exclusive arguments with optional and positional argument

Question

I would like to get this with argparse library :

PROG --yesterday | begin-date [end-date]

I tried to combine mutual exclusion and argument

Answer 1

--yesterday is redundant, since it is just a shortcut for setting start_date to yesterday's day. Instead, let "yesterday" be an allowable value for start_date. In fact, you can generalize datetime to allow other abbreviations, for either argument, as desired. For example:

def argument_date(str_date):
    # Not the most efficient to roundtrip like this, but
    # fits well with your existing code
    now = datetime.datetime.utcnow().date()
    if str_date == "yesterday":
        str_date = str(now - datetime.timedelta(1))
    elif str_date == "today"
        str_date = str(now)

    try:
        return datetime.strptime(str_date, "%Y-%m-%d").replace(tzinfo=pytz.utc)
    except ValueError as e:
        raise argparse.ArgumentTypeError(e)

Once you've done this, your code simply becomes:

parser = argparse.ArgumentParser(prog='PROG')
parser.add_argument('start', type=argument_date, help='Start date (YYYY-MM-DD, yesterday, today)')
parser.add_argument('end', type=argument_date, nargs='?', help='End date (YYYY-MM-DD, yesterday, today)')