Just a small code to encrypt and decrypt caesar cypher.

caesar_cypher.py

LETTERS = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'

def encrypt(string, shift=1):
    '''
    Caesar Cypher shifts the letters by the given shift, for example, if key=1
    then, a becomes b, be becomes c, and c becomes d, etc
    '''
    assert 1<=shift<26
    words = string.split() #Splitting by spaces
    words_list = []
    for word in words:
        current_word = ''
        for letter in word:
            letter = letter.upper()
            index = LETTERS.index(letter)+shift
            current_word += LETTERS[index%26]
        words_list.append(current_word)
    return ' '.join(words_list)

def decrypt(string, shift):
    words = []
    for word in string.split():
        print(f'Current word: {word}')
        current_word = ''
        for letter in word:
            index = LETTERS.index(letter)
            current_word += LETTERS[index-shift]
        words.append(current_word)
    return ' '.join(words)