why is python argparse giving the help for imported module rather than current module?

i have these two simple files: this is tone.py:

import argparse
import os
import sys
root , pyfilename = os.path.split(os.path.abspath(__file__))

try:
    parser = argparse.ArgumentParser()
    parser.add_argument('--argone', help='argument one',default= "one" )
    parser.add_argument('--argtwo', help='argument two',default= "two" )
    parser.add_argument('--argthree', help='argument three',default= "three" )
    parser.add_argument('--argfour', help='argument three',default=False )
    args = parser.parse_args()
except Exception as e:
    print "crapped"

class One():
    pass

if __name__ == "__main__" :
    while True:
        print (args.argone)
        print (args.argtwo)
        print (args.argthree)

and this is ttwo.py:

import argparse
import os
import sys
root , pyfilename = os.path.split(os.path.abspath(__file__))

try:
    from tone  import One
except Exception as e:
    print "cant import module coz: %s ; so i'm exiting"%e
    sys.exit()


try:
    import defaults
    parser = argparse.ArgumentParser()
    parser.add_argument('--arga', help='arga',default= "a" )
    parser.add_argument('--argb', help='argb',default= "b" )
    parser.add_argument('--argc', help='argc',default= "c" )
    parser.add_argument('--argd', help='targd',default=False )
    args = parser.parse_args()
except Exception as e:
    print "crapped"


if __name__ == "__main__" :
    print (args.arga)
    print (args.argb)
    print (args.argc)

now if i run tone.py with the help switch i get what i expect:

$ python  tone.py -h 
usage: tone.py [-h] [--argone ARGONE] [--argtwo ARGTWO] [--argthree ARGTHREE]
               [--argfour ARGFOUR]

optional arguments:
  -h, --help           show this help message and exit
  --argone ARGONE      argument one
  --argtwo ARGTWO      argument two
  --argthree ARGTHREE  argument three
  --argfour ARGFOUR    argument three

but the second one gives unexpected results:

$ python  ttwo.py -h 
usage: ttwo.py [-h] [--argone ARGONE] [--argtwo ARGTWO] [--argthree ARGTHREE]
               [--argfour ARGFOUR]

optional arguments:
  -h, --help           show this help message and exit
  --argone ARGONE      argument one
  --argtwo ARGTWO      argument two
  --argthree ARGTHREE  argument three
  --argfour ARGFOUR    argument three

this is the help for the first module. what happened? and how do i fix it?