Question

创建将字符串编码为不同字符串的程序

def encode(letters,code,word):
    lettersTab = list(letters)
    lettersTab = lettersTab*2
    lenghtLetters = len(letters)
    howMany = code%lenghtLetters
    wordTab = list(word)
    secondTab = [None]*len(word)
    for j in range(0,len(word)):
        for i in range(0,int(len(lettersTab)/2)):
            secondTab[j] = wordTab[j].replace(lettersTab[i],lettersTab[i+howMany])
    print(secondTab)
encode("bca",2,"abc")

该输入意味着b转换为a等，b-> a，c-> b，a-＆gt; c

输出应为：

['c','a','b']

但它是

['b','b','c']

Answer 1

由于内循环

，您的算法无法达到预期效果

for i in range(0,int(len(lettersTab)/2)):

正在循环的每一步设置secondTab[j]到wordTab[j]，即使wordTab[j]与lettersTab[i]不匹配，这也不是您想要的。

请注意，如果newstr = oldstr.replace(a, b)不包含newstr，则oldstr会oldstr = a。

所以这里是你的功能的清理版本，加上几个渐进式改进，最后的例子使用列表理解。我的一些版本使用index()，如果它找不到它正在寻找的东西会抛出异常，但是你的原始代码会遇到类似的问题。

我更改了函数的名称，因为encode是Python 2中的标准字符串函数（我正在运行）。

#! /usr/bin/env python

'''
Caeser encryption
From http://stackoverflow.com/questions/25950099/my-program-dont-work-i-dont-know-why
'''

import sys

def caeser_encode0(letters, code, word):
    lettersTab = list(letters) * 2
    howMany = code % len(letters)
    wordTab = list(word)
    secondTab = [None] * len(word)
    for j in range(0, len(word)):
        for i in range(0, int(len(lettersTab)/2)):
            if wordTab[j] == lettersTab[i]:
                secondTab[j] = wordTab[j].replace(lettersTab[i], lettersTab[i + howMany])
                print(wordTab[j], lettersTab[i], lettersTab[i + howMany], secondTab)
    print(secondTab)


def caeser_encode1(letters, code, word):
    lettersTab = list(letters) * 2
    howMany = code % len(letters)
    wordTab = list(word)
    secondTab = []
    for ch in word:
        for i in range(0, int(len(lettersTab)/2)):
            if ch == lettersTab[i]:
                secondTab.append(lettersTab[i + howMany])
                print(ch, lettersTab[i], lettersTab[i + howMany], secondTab)
    print(secondTab)


def caeser_encode2(letters, code, word):
    lettersTab = list(letters) * 2
    howMany = code % len(letters)
    secondTab = []
    for ch in word:
        i = lettersTab.index(ch)
        secondTab.append(lettersTab[i + howMany])
        print(ch, lettersTab[i], lettersTab[i + howMany], secondTab)
    print(secondTab)


def caeser_encode3(letters, code, word):
    howMany = code % len(letters)
    secondTab = []
    for ch in word:
        i = letters.index(ch)
        newi = (i + howMany) % len(letters)
        secondTab.append(letters[newi])
        print(ch, letters[i], letters[newi], secondTab)
    print(secondTab)


def caeser_encode4(letters, code, word):
    howMany = code % len(letters)
    secondTab = []
    for ch in word:
        newi = (letters.index(ch) + howMany) % len(letters)
        secondTab.append(letters[newi])
        print(ch, letters[newi], secondTab)
    print(secondTab)


def caeser_encode(letters, code, word):
    howMany = code % len(letters)
    secondTab = [
        letters[(letters.index(ch) + howMany) % len(letters)] for ch in word]
    print(secondTab)


def main():
    caeser_encode("bca", 2, "abc")

if __name__ == '__main__':
    main()

希望您（或某人:)）将从这些示例中了解有关Python的更多信息......

我的计划不起作用，我不知道为什么

1 个答案: