######################
driver1.py
import argparse
import sys
import a1
import b1

def build_parser():
    parser = argparse.ArgumentParser()

    parser.add_argument('-a',action='store',dest='a')
    parser.add_argument('-b',action='store',dest='b')
    return parser

def driver(args):
    print type(args)
    print args
    a1.main(args)
    b1.main(args)

def main(args):
    parser = build_parser()
    args = parser.parse_known_args(args)
    driver(args)

if __name__ == "__main__":
    main(sys.argv)
####################
a1.py
import argparse
import sys

def build_parser():
    parser = argparse.ArgumentParser()

    parser.add_argument('-a',action='store',dest='a')
    return parser

def driver(args):
    print type(args)
    print args

def main(args):
    parser = build_parser()
    args = parser.parse_known_args(args)
    driver(args)

if __name__ == "__main__":
    main(sys.argv)
####################
b1.py
import argparse
import sys

def build_parser():
    parser = argparse.ArgumentParser()

    parser.add_argument('-b',action='store',dest='b')
    return parser

def driver(args):
    print type(args)
    print args

def main(args):
    #parser = build_parser()
    #args = parser.parse_args(args)
    driver(args)

if __name__ == "__main__":
    main(sys.argv)