CS50 Ceaser python

ceaser.py

from cs50 import cs50

alphabet = "abcdefghijklmnopqrstuvwxyz"
alphabetcap = alphabet.upper()
cyphertext = ""

word = input("Please enter in a word to be encrypted: ")

key = int(input("Please enter a numnber to use as the encryption key: "))

for letter in word:
    if letter in alphabet:
        newposition = (alphabet.find(letter) + key) % 26
        cyphertext += alphabet[newposition]

    elif letter in alphabetcap:
        newposition = (alphabetcap.find(letter) + key) % 26
        cyphertext += alphabetcap[newposition]

    else:
        cyphertext += letter

print(cyphertext)