Caesar Cipher Python

import sys

def encrypt(k):
    plaintext = raw_input('Enter plain text message: ')
    cipher = ''

    for each in plaintext:
        c = (ord(each)+k) % 126

        if c < 32:
            c+=31

        cipher += chr(c)

    print 'Your encrypted message is: ' + cipher

def decrypt(k):
    cipher = raw_input('Enter encrypted message: ')
    plaintext = ''

    for each in cipher:
        p = (ord(each)-k) % 126

        if p < 32:
            p+=95

        plaintext += chr(p)

    print 'Your plain text message is: ' + plaintext

def main(argv):
    if (len(sys.argv) != 3):
        sys.exit('Usage: ceaser.py <k> <mode>')

    if sys.argv[2] == 'e':
        encrypt(int(sys.argv[1]))
    elif sys.argv[2] == 'd':
        decrypt(int(sys.argv[1]))
    else:
        sys.exit('Error in mode type')


if __name__ == "__main__":
    main(sys.argv[1:])