What algorithm to use to encrypt with a key (string)?

Question

Python

There is a string of 30 characters - used as a key for encryption and decryption. You need to encrypt and decrypt another string of indeterminate length using the key string.
What is the best algorithm to use for this option?

Answer 1

xor

Answer 2

Better is a loose concept. Adding each byte of the input text to the byte of your key is a good algorithm, simple.