caesar.py

#!/usr/bin/python


s_ascii =   [97,98,99,100,101,102,103,104,105,106,107,108,109,110,111,112,113,114,115,116,117,118,119,120,121,122]
b_ascii =   [65,66,67,68,69,70,71,72,73,74,75,76,77,78,79,80,81,82,83,84,85,86,87,88,89,90]


    
def caesar_crypt(source,target,k):
    
    file = open(source,"r")
    temp=""
    for i in file:
        for s in i:
            temp +=caesar_char_crypt(s,k)
    
    file.close
    file=open(target,"w")
    file.write(temp)
    file.close
    
    return
def caesar_decrypt(source,target,k):
    
    file = open(source,"r")
    temp=""
    for i in file:
        for s in i:
            temp +=caesar_char_decrypt(s,k)
    
    file.close
    file=open(target,"w")
    file.write(temp)
    file.close
    
    return

def caesar_char_decrypt(char,k):

    for i in range(26):
        if ord(char)==s_ascii[i] :
            return chr(int(s_ascii[(i-k)%25]))
        if ord(char)==b_ascii[i] :
            return chr(int(b_ascii[(i-k)%25]))
    
    return char

def caesar_char_crypt(char,k):
    for i in range(26):
        if ord(char)==s_ascii[i] :
            return chr(int(s_ascii[(k+i)%25]))
        if ord(char)==b_ascii[i] :
            return chr(int(b_ascii[(k+i)%25]))
    
    return char


def main():
    caesar_crypt("plain_text.txt","encoded_text.txt",3)
    caesar_decrypt("encoded_text.txt","new_plain_text.txt",3)
    
                

main()