加密和解密例子

# -*- coding:utf-8 -*-

def extract(line, sep=' '):
    
    line = line.strip()
    line = line.upper()
    words = line.split(sep)
    #print(words)
    
    if line == '':
        return 'Missing key!','Missing text!'
    elif len(words) == 1 and words[0] != '':
        key = words[0]
        return key,'Missing text!'
    elif len(words) == 2:
        key = int(words[0])
        word = words[1]
        return key,word


def encrypted(key, word):
    result = ''
    length = 26
    for item in word:
        index = ord(item)
        tmp = index - 65 + key
        
        tmp = tmp % 26
        char = chr(tmp+65)
        
        result = result + char
    return result

def deencrypted(key, ciphertext):
    result = ''
    length = 26
    for item in ciphertext:
        index = ord(item)
        tmp = index-65-key
        tmp = (tmp + 26)%26
        char = chr(tmp+65)
        result = result + char
    return result

def main():
    
    #filename = input('Enter the input filename:')
    filename = 'secret_code.txt'

    if len(filename) > 0:
        with open(filename, 'r') as file:
            data = file.readlines()
            for line in data:
                key,word = extract(line,sep=' ')
                #print('key={} word={}'.format(key, word))
                if key=='Missing key!' and word == 'Missing text!':
                    continue
                
                if word == 'Missing text!':
                    print('Missing text!')
                    
                if key != 'Missing key!' and word != 'Missing text!':
                    print(deencrypted(key, word))

if __name__ == '__main__':
    main()