如何通过字母位置增加列表中字母的位置？

Question

我有一个程序，它取一个字母的位置，并通过移位的值增加位置，然后给我新的字母位置，这是一个凯撒列表功能。但是我需要能够通过shift的值以及字母的位置来增加字母的位置，所以如果我有“你好”并且shift为15，则h = 7所以7 + 15 + 0 = 22并且e将是4 + 15 + 1（e的位置）= 20但是，我不确定如何编辑我的代码，以便我可以通过其位置的值增加每个字母的位置。代码工作正常，我只需要帮助搞清楚这一步。

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'] 
def caesar(plaintext,shift):  
# initialize ciphertext as blank string
    ciphertext = ""
# loop through the length of the plaintext
    for i in range(len(plaintext)):        
    # get the ith letter from the plaintext
        letter = plaintext[i]
    # find the number position of the ith letter
        num_in_alphabet = alphabet.index(letter)
        print (num_in_alphabet)
    # find the number position of the cipher by adding the shift 
        cipher_num = (num_in_alphabet + shift + 3) % len(alphabet) 
    # find the cipher letter for the cipher number you computed
        cipher_letter = alphabet[cipher_num] 
    # add the cipher letter to the ciphertext
        ciphertext = ciphertext + cipher_letter 

# return the computed ciphertext
    return ciphertext
def main():

    plaintext = ("hello")
    shift = 16

    text = caesar(plaintext,shift)
    print (text)

main()

Answer 1

cipher_num = (num_in_alphabet + shift + i) % len(alphabet) 

或者更简单

shift = 16
chiper =  ''.join([chr(((ord(c)-ord('a')+shift+i)%26)+ord('a')) for i, c in enumerate("hellow")])
assert  chiper == 'xvdeir'