encryptDecrypt.py

import random, unittest

def generateMagicKey():
    magicKey = {}
    list1 = ["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"]
    list2 = ["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"]
    while len(list2) > 0:
        z = random.randint(0, len(list2)-1)
        y = random.randint(0, len(list2)-1)
        a, b = list1[z], list2[y]
        magicKey[a], magicKey[b] = b, a
        list1.remove(a)
        list2.remove(a)
        try: list2.remove(b)
        except: pass
        try: list1.remove(b)
        except: pass

    print "Your magic key is:\n"
    print magicKey
    return magicKey

def encrypt(word, magicKey):
    stringBuild = ""
    for i in word:
        i = i.lower()
        if i in magicKey.keys(): stringBuild += magicKey[i.lower()]
        else: stringBuild += i
    return stringBuild

def decrypt(word, magicKey):
    stringBuild = ""
    for i in word:
        if i in magicKey.keys(): stringBuild += magicKey[i]
        else: stringBuild += i
    return stringBuild
    
class Test_phrases(unittest.TestCase):
    s = "Sunshine, daisies, butter mellow, turn this stupid, fat rat yellow."
    print(s)
    magicKey = generateMagicKey()
    newWord = encrypt(s, magicKey)
    print(newWord)

    def test_poem(self):
        decrypted = decrypt(self.newWord, self.magicKey)
        print(decrypted)
        self.assertEqual(decrypted, self.s.lower())

if __name__ == "__main__":
    unittest.main()

Added ability to encrypt and decrypt phrases.