Caesar Cipher-Python

Question

我最近做了一项任务，我的教授说明了它是不是100％正确，但我不确定如何解决这个问题。他对我的hw的回复是＆＃34;尝试29或55的密钥。而不是使用ord，使用ALPHABET字符串中的字母索引。＆＃34;现在我对编程很陌生，所以任何一条建议都会有所帮助。需要帮助找出要做的事情。

代码：

def circularShift(text, key):
    ALPHABET = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
    text = text.upper()
    shiftedTextSoFar =" "
    for letter in text:
        shifted = ord(letter) + key
        if (shifted < 65):
            shifted += 26
        if (shifted > 90):
            shifted -= 26
        shiftedTextSoFar +=chr(shifted)
    return shiftedTextSoFar
print (circularShift("MOLLOY", 3)) #SHOULD PRINT PROORB
print (circularShift("PROOB", - 3)) # SHOULD PRINT MOLLOY

Answer 1

以下是代码的改进版本，使用index建议：

def circularShift(text, key):
    ALPHABET = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
    shiftedTextSoFar =" "
    # you can also change text to upper during for/loop
    for letter in text.upper():
        # should do a try/except here really in case user input invalid text
        # using string index to return index value
        # using (key % len(ALPHABET)) will reduce key length of any 26's multiples
        shifted = ALPHABET.index(letter) + (key % len(ALPHABET))

        # if after adjusting shifted is out of index, reduce by 26 i.e len(ALPHABET)
        if shifted > len(ALPHABET):
            shifted -= len(ALPHABET)
        # Python already has -ve index taken care, ie. ALPHABET[-1] = 'Z'
        shiftedTextSoFar += ALPHABET[shifted]
    return shiftedTextSoFar

print (circularShift("MOLLOY", 29)) #SHOULD PRINT PROORB
print (circularShift("PROOB", 55)) # SHOULD PRINT MOLLOY
 PROORB
 SURRE