Convert decimal 2 binary

dec2bin.py

#!/usr/bin/python

import sys,re
from optparse import OptionParser

def dec2bin(target):
    result = []
    mask = 1
    shift = 0
    while mask <= target:
        bit = (target & mask) >> shift
        result.append(str(bit))
        mask <<= 1
        shift += 1
    return "".join(reversed(result))

def dec2hex(target):
    result = []
    hexstr = "0123456789ABCDEF"
    mask = 15
    shift = 0
    while mask <= target:
        bits = (target & mask) >> shift
        result.append(hexstr[bits])
        mask <<= 4
        shift += 4
    bits = (target & mask) >> shift
    result.append(hexstr[bits])
    return "".join(reversed(result))

def parse_args():
    parser = OptionParser()
    parser.add_option("-b", "--binary", action = "store_true", default = False)
    parser.add_option("-p", "--padding", action = "store_true", default = False)
    opt, args = parser.parse_args()
    argcheck = True
    for arg in args:
        if not re.match("^\d*$", arg):
            argcheck = False
            break
    return argcheck, opt, args

if __name__ == "__main__":
    argcheck, opt, args = parse_args()
    if not argcheck:
        print("Error: every arguments must be integer.")
    else:
        converter = dec2bin if opt.binary else dec2hex
        result = [converter(int(arg)) for arg in args]
        if opt.padding:
            maxlen = max((len(item) for item in result))
            a,b = divmod(maxlen, 8)
            padding_size = 8 * a if not b else 8 * (a + 1)
            for res in result:
                print(res.rjust(padding_size, "0"))
        else:
            for res in result:
                print(res)