Encoding and Decoding | Python Fiddle

alpha = ["a","b","c","d","e","f","g","h","i","j","k","l","m","n","o","p","q","r","s","t","u","v","w","x","y","z" ," "]
cypher_alpha = []

def encode(message,cypher_alpha,alpha):
    coded_message = []
    for i in range(len(message)):
        for j in range(len(alpha)):
            if message[i] == alpha[j]:
                coded_message.append(cypher_alpha[j])
        cypher_alpha.append(cypher_alpha.pop(0))
        
    return coded_message    
        
def decode(message,cypher_alpha,alpha):
    decoded_message = []
    for i in range(len(message)):
        for j in range(len(cypher_alpha)):
            if message[i] == cypher_alpha[j]:
                decoded_message.append(alpha[j])
        cypher_alpha.append(cypher_alpha.pop(0))
        
    return decoded_message

while True:
    keyword = raw_input("Enter you Keyword:\n")
    key = []
    for i in keyword:
        if i not in key:
            key.append(i)
    for i in key:
	    cypher_alpha.append(i)
    for i in alpha:
        if i not in cypher_alpha:
            cypher_alpha.append(i)
    message = raw_input("Enter your message:\n")
    encrypt = raw_input("encode or decode?\n")
    if encrypt == "encode":
    	coded_message = encode(message,cypher_alpha,alpha)
    elif encrypt == "decode":
    	coded_message = decode(message,cypher_alpha,alpha)
    
    coded_message = "".join(coded_message)
    print coded_message
    repeat = raw_input("repeat?\n")
    if repeat == "no":
        break

Browser Version Not Supported

Due to Python Fiddle's reliance on advanced JavaScript techniques, older browsers might have problems running it correctly. Please download the latest version of your favourite browser.
Chrome 10+ Firefox 4+ Safari 5+
IE 10+

Let me try anyway!

Python Fiddle

Python Cloud IDE