Cryptography in Python

[NLittle17]

print("CryptoPrac-1a.")

for x in range(97, 123): # 97 starts the lowercase alphabet and 122 is z (ending)
  print(chr(x), end = ' ')
print('\n')
for x in range(97, 123):
  print(chr(x + 3), end = ' ')


print("\n CryptoPrac-1b.")

I am trying to add to the second part of this code. What I am trying to do is keep the shift by three but only this time I am trying to use the modulus operator. I am using the ASCII table but I don't know how to start a for loop to do what I want to do .