[FIXED] How to specify a minimum or maximum float value with argparse

Issue

How can I specify a minimum or maximum floating point argument using argprase? I'd like to be able to provide a command-line argument between a min and max floating point value.

The closest thing I can find is the choices option in add_argument(), but that only specifies allowable values for the argument.

parser.add_argument("L", type=float, choices=range(2))

The command-line argument 0.5 for L fails:

invalid choice: 0.5 (choose from 0, 1)

Solution

You can (and should) use a custom type function. It's much more user friendly.

def range_limited_float_type(arg):
    """ Type function for argparse - a float within some predefined bounds """
    try:
        f = float(arg)
    except ValueError:    
        raise argparse.ArgumentTypeError("Must be a floating point number")
    if f < MIN_VAL or f > MAX_VAL:
        raise argparse.ArgumentTypeError("Argument must be < " + str(MAX_VAL) + "and > " + str(MIN_VAL))
    return f



parser.add_argument(
    '-f',
    '--float',
    type=range_limited_float_type,
    help='Your argument description'
)

Answered By - rdas