Enciphering and Deciphering by Shuffling in Python

I am writing a program that enciphers (and will eventually decipher) a given string.

The encipher function takes two arguments: the string and a seed value.

Here is what I have so far:

def random_encipher(string,seed):

seed = random.seed(seed)

alphabet = ["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"]

#shuffle alphabet
random.shuffle(alphabet)

#assign index to each letter in alphabet
for letter in alphabet:
    letter = ord(letter)-97

To sum all that up, basically I'm shuffling the alphabet and assigning each letter a number value ("a" = 0, "b" = 1, . . .)

Here's what I need help with:

I need string[0] to be printed as alphabet[0] (which is the shuffled alphabet, therefore with the current seed value, alphabet[0] = "e").

But for each letter of the string, not just the zero index.

Any help would be greatly appreciated.