Test if string ONLY contains given characters

Question

What\'s the easiest way to check if a string only contains certain specified characters in Python? (Without using RegEx or anything, of course)

Specifically, I have

Answer 1

You can make use of sets:

>>> l = ['aba', 'acba', 'caz']
>>> s = set('abc')
>>> [item for item in l if not set(item).difference(s)]
['aba', 'acba']