#!/usr/bin/env python
import argparse

def number_triple(string):
    fields = string.strip().split()

    if len(fields) != 3:
        print '"%s"' % string
        raise argparse.ArgumentTypeError('Need exactly 3 numbers')

    try:
        ret = (int(fields[0]), int(fields[1]), float(fields[2]))
    except ValueError:
        raise argparse.ArgumentTypeError('Need exactly 3 numbers')

p = argparse.ArgumentParser(description='Reproduce argparse type bug')
p.add_argument('-t', '--triple', metavar='N', nargs=3, type=number_triple)

args = p.parse_args('-t 1 2 3'.split())
print args