Compare two one line files bit by bit

bitCmp.py

import os
import argparse

def tobits(s):
    result = []
    for c in s:
        bits = bin(ord(c))[2:]
        bits = '00000000'[len(bits):] + bits
        result.extend([int(b) for b in bits])
    return result

def frombits(bits):
    chars = []
    for b in range(len(bits) / 8):
        byte = bits[b*8:(b+1)*8]
        chars.append(chr(int(''.join([str(bit) for bit in byte]), 2)))
    return ''.join(chars)

parser = argparse.ArgumentParser(description='Easy way to produce plots of\
3D vector fields in python.')
parser.add_argument("files", nargs = 2,
                    help='Two Files to compare',
                    type=str)
args = parser.parse_args()

f_1 = open(args.files[0], 'r')
f_2 = open(args.files[1], 'r')

bitString1 = tobits(f_1.readline())
bitString2 = tobits(f_2.readline())

same = 0
diff = 0
length = len(bitString1)

for i in range(len(bitString1)):
    if bitString1[i] == bitString2[i]:
        same += 1
    else:
        diff += 1

print "Bits the same: ", same
print "Bits different: ", diff
print "Percent Differnet: ", float(diff) / float(length)