The title pretty much summarizes what I'd like to have happen.
Here is what I have, and while the program doesn't blow up on a nonpositive integer, I want the user to be informed that a nonpositive integer is basically nonsense.
import argparse
parser = argparse.ArgumentParser()
parser.add_argument("-g", "--games", type=int, default=162,
help="The number of games to simulate")
args = parser.parse_args()
And the output:
python simulate_many.py -g 20
Setting up...
Playing games...
....................
Output with a negative:
python simulate_many.py -g -2
Setting up...
Playing games...
Now, obviously I could just add an if to determine if args.games
is negative, but I was curious if there was a way to trap it at the argparse
level, so as to take advantage of the automatic usage printing.
Ideally, it would print something similar to this:
python simulate_many.py -g a
usage: simulate_many.py [-h] [-g GAMES] [-d] [-l LEAGUE]
simulate_many.py: error: argument -g/--games: invalid int value: 'a'
Like so:
python simulate_many.py -g -2
usage: simulate_many.py [-h] [-g GAMES] [-d] [-l LEAGUE]
simulate_many.py: error: argument -g/--games: invalid positive int value: '-2'
For now I'm doing this, and I guess I'm happy:
if args.games <= 0:
parser.print_help()
print "-g/--games: must be positive."
sys.exit(1)
This should be possible utilizing type
. You'll still need to define an actual method that decides this for you:
def check_positive(value):
ivalue = int(value)
if ivalue <= 0:
raise argparse.ArgumentTypeError("%s is an invalid positive int value" % value)
return ivalue
parser = argparse.ArgumentParser(...)
parser.add_argument('foo', type=check_positive)
This is basically just an adapted example from the perfect_square
function in the docs on argparse
.