caesar_cipher.py

def caesar_encrypt(realText, step):
	outText = []
	cryptText = []
	
	uppercase = ['A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z']
	lowercase = ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z']

	for eachLetter in realText:
		if eachLetter in uppercase:
			index = uppercase.index(eachLetter)
			crypting = (index + step) % 26
			cryptText.append(crypting)
			newLetter = uppercase[crypting]
			outText.append(newLetter)
		elif eachLetter in lowercase:
			index = lowercase.index(eachLetter)
			crypting = (index + step) % 26
			cryptText.append(crypting)
			newLetter = lowercase[crypting]
			outText.append(newLetter)
	return outText

code = caesar_encrypt('abc', 2)
print(code)

What do you think about this logic is it missing something or does the job?

actual_data = input("Enter the string to cipher using ceaser encryption ")
selection_shift = input ('Enter the type of shift you want to apply [Left | Right] ')
encrypted_data=''
if selection_shift.lower()=='left':
n = int(input('no of characters to shift by '))
for x in actual_data:
encrypted_data += x.replace(x,chr(ord(x)-n))
else:
n = int(input('no of characters to shift by '))
for x in actual_data:
encrypted_data += x.replace(x,chr(ord(x)+n))
print(encrypted_data)

(crypting = (index + step) % 26) in the above code, what is the role of "% 26". How does it work to give the right answer?