How to find if a string has a character which isn't in another string

Question

For example I can have the string 'acagtcas' and I want to find if the string has any characters that aren't a, c, g or t. I've tried using not but I haven't been able to make it work. How can I implement this?

Answer 1

You can use set.difference:

s = "acagtcas"

x = set(s).difference("acgt")
print(x)

Prints:

{'s'}