用 Python 简化 Vigenere 密码程序

Posted 2023-02-16

【中文标题】用 Python 简化 Vigenere 密码程序

【英文标题】：Simplifying Vigenere cipher program in Python

【发布时间】：2016-05-12 20:16:12

【问题描述】：

我有下面的程序，它被传递给另一个函数，该函数简单地打印出原始和加密的消息。我想知道如何简化这个程序，特别是“match = zip”和“change = (reduce(lambda”) 行。如果可以在不使用 lambda 的情况下做到这一点，我该怎么做？

from itertools import cycle

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 vigenereencrypt(message,keyword):
    output = ""    
    match = zip(message.lower(),cycle(keyword.lower()))
    for i in match:
        change = (reduce(lambda x, y: alphabet.index(x) + alphabet.index(y), i)) % 26
        output = output + alphabet[change]
    return output.lower()

【参考方案1】：

两件事：

你不需要有一个局部变量match，只需循环zip 您可以在 for 循环定义中拆分两个索引 x 和 y，而不是使用 reduce； reduce 通常用于较大的可迭代对象，由于 i 中只有 2 个项目，因此会增加不必要的复杂性。

即，您可以将 for 循环定义更改为：

for x, y in zip(...):

以及您对change 的定义：

change = (alphabet.index(x) + alphabet.index(y)) % 26

【参考方案2】：

从R Nar所说的开始：

def vigenereencrypt(message,keyword):
    output = ""
    for x, y in zip(message.lower(), cycle(keyword.lower())):
        change = (alphabet.index(x) + alphabet.index(y)) % 26
        output = output + alphabet[change]
    return output.lower()

我们可以通过使用列表然后加入它来提高效率，而不是添加到字符串中，并且还可以通过注意输出已经是小写：

def vigenereencrypt(message,keyword):
    output = []
    for x, y in zip(message.lower(), cycle(keyword.lower())):
        change = (alphabet.index(x) + alphabet.index(y)) % 26
        output.append(alphabet[change])
    return "".join(output)

然后我们可以将循环体减少到一行..

def vigenereencrypt(message,keyword):
    output = []
    for x, y in zip(message.lower(), cycle(keyword.lower())):
        output.append(alphabet[(alphabet.index(x) + alphabet.index(y)) % 26])
    return "".join(output)

...所以我们可以把它变成一个列表推导：

def vigenereencrypt(message,keyword):
    output = (
        alphabet[(alphabet.index(x) + alphabet.index(y)) % 26]
        for x, y in zip(message.lower(), cycle(keyword.lower()))
    )
    return "".join(output)

我觉得我们可以用 map(alphabet.index, ...) 做一些事情，但我想不出比列表理解更好的方法。

【参考方案3】：

你可以用一堆索引而不是 zip 来做到这一点......

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"]
alphaSort = k:n for n,k in enumerate(alphabet)
alphaDex = n:k for n,k in enumerate(alphabet)

def vigenereencrypt(message,keyword):
    output = ""    
    #match = zip(message.lower(),cycle(keyword.lower()))      # zip(a,cycle(b)) Creates [(a[n],b[n%len(b)]) for k in range(len(a)) ] 
    op = ""                                                  # So lets start with  for k in range(len(a))
    for k in range(len(message)):
        op += alphaDex[(alphaSort[message.lower()[k]]+alphaSort[keyword.lower()[k%len(keyword)]])%len(alphabet)]
    return(op)