将两个相似的函数泛化为一个

Question

所以下面是一些能够对句子进行编码和解码的 Python 代码。我不确定如何定义一个函数，该函数采用三个参数来概括或组合这两个函数：mapInToOutEncode 和 mapInToOutDecode 合二为一。

alphabet = " abcdefghijklmnopqrstuvwxyz"
keyString ="kjihgfedcba zyxwvutsrqponml"

def mapInToOutEncode(inChar):
    index = 0
    found = 0
    for char in alphabet:
        if(char == inChar):
            found = index #remember it in a variable found
        else:
            index +=1
    outChar = keyString[found]
    return(outChar)

def mapInToOutDecode(inChar):
    index = 0
    found = 0
    for char in alphabet:
        if(char == inChar):
            found = index #remember it in a variable found
        else:
            index +=1
    outChar = keyString[found]
    return(outChar)

def encode(inString):
    outString = ''
    for char in inString:
        outString += mapInToOutEncode(char)
    return(outString)

def decode(inString):
    outString = ''
    for char in inString:
        outString += mapInToOutDecode(char)
    return(outString)

print( encode("this is a crazy bit of news to share we attack at dawn" ))
print( decode(encode("this is a crazy bit of news to share we attack at dawn")))

Answer 1

首先，请注意您的函数 mapInToOutEncode 和 mapInToOutDecode 是相同的。为了获得您想要的功能，mapInToOutDecode 应该是：

def mapInToOutDecode(inChar):
    index = 0
    found = 0
    for char in keyString:
        if(char == inChar):
            found = index #remember it in a variable found
            break
        else:
            index +=1
    outChar = alphabet[found]
    return(outChar)

请注意，我还添加了单词 break，因此您的代码一旦找到它就不会继续寻找 inchar。

现在，要获得您想要的（mapInToOutEncode 和 mapInToOutDecode 的通用函数），您可以：

def mapInToOut(inChar, alphFrom, alphTo):
    index = 0
    found = 0
    for char in alphFrom:
        if(char == inChar):
            found = index #remember it in a variable found
            break
        else:
            index +=1
    outChar = alphTo[found]
    return(outChar)

要编码每个字符a，您将使用mapInToOut(a, alphabet, keyString)。要解码每个字符 b，您可以使用 mapInToOut(b, keyString, alphabet).

因此，encode 和 decode 函数将如下所示：

def encode(inString):
    outString = ''
    for char in inString:
        outString += mapInToOut(char, alphabet, keyString)
    return(outString)

def decode(inString):
    outString = ''
    for char in inString:
        outString += mapInToOut(char, keyString, alphabet)
    return(outString)

这是一个 完整的 工作示例（即，这应该是您的全部代码）：

alphabet = " abcdefghijklmnopqrstuvwxyz"
keyString ="kjihgfedcba zyxwvutsrqponml"

def mapInToOut(inChar, alphFrom, alphTo):
    index = 0
    found = 0
    for char in alphFrom:
        if(char == inChar):
            found = index #remember it in a variable found
            break
        else:
            index +=1
    outChar = alphTo[found]
    return(outChar)

def encode(inString):
    outString = ''
    for char in inString:
        outString += mapInToOut(char, alphabet, keyString)
    return(outString)

def decode(inString):
    outString = ''
    for char in inString:
        outString += mapInToOut(char, keyString, alphabet)
    return(outString)

print ("this is a crazy bit of news to share we attack at dawn")
encoded_msg = encode("this is a crazy bit of news to share we attack at dawn")
print encoded_msg
print decode(encoded_msg)

Answer 2

尝试使用字典来做你的encoding/decoding，它会大大简化你的代码：

>>> alphabet = " abcdefghijklmnopqrstuvwxyz"
>>> keyString ="kjihgfedcba zyxwvutsrqponml"
>>> encoder = dict(zip(alphabet, keyString))
>>> decoder = dict(zip(keyString, alphabet))
>>> a = 'this is a string'
>>> q = ''.join(encoder.get(i, i) for i in a)
>>> q
'rcbskbskjksrtbxd'
>>> ''.join(decoder.get(i, i) for i in q)
'this is a string'

将两个相似的函数泛化为一个

Generalizing two similar functions into one

python

string

python-3.x

decode

encode