Question

Write a Python program that reads text from a file, encrypts it with a Caesar Cipher, and displays the encrypted text. Do not process punctuation. Convert the original string to all lower-case before encrypting it.

Answer 1

# dictionary with key as alphabets value as numbers pairs
d = {
    'a': 0, 'b': 1, 'c': 2, 'd': 3, 'e': 4, 'f': 5, 'g': 6, 'h': 7, 'i': 8, 'j': 9,
    'k': 10, 'l': 11, 'm': 12, 'n': 13, 'o': 14, 'p': 15, 'q': 16, 'r': 17, 's': 18,
    't': 19, 'u': 20, 'v': 21, 'w': 22, 'x': 23, 'y': 24, 'z': 25
}
list1 = []  # initilaize an empty list
with open('filetext.txt', 'r') as f:  # read file
    for i in f.readlines(): # for each line in file append it to the list1
        for j in i.splitlines():
            list1.append(j)
n = int(input('Enter the value for shift key '))  # enter any number as shift key both sender and receiver should compromise on this key
for line in list1: # for each line in list1 convert it to lower case letters
    str2 = ''
    for i in line.lower():
        if i == ' ' or i == '!' or i == '@' or i == '#' or i == '$' or i == '%' or i == '&' or i == '*' or i == '^': # if i is any punctuation then append as is
            str2 += i
        else:
            jk = (d[i] + n) % 26  # else find the value for the letter
            for k, j in d.items():  # compare the value with the dict value
                if j == jk:  # if both matches then get the key and append it to the str2
                    str2 += k
    print("The encrypted value for the word ", line.lower(), ' is ', str2, '\n')

filetext.txt file