How to check if a string contains only characters from a given set in python

Question

I have a a user-inputted polynomial and I only want to use it if it only has characters in the string 1234567890^-+x.

How can I check if it does or not

Answer 1

What about just convert both the string into set and checking input_set is subset of good_set as below:

>>> good_set = set('1234567890^-+x')
>>> input_set1 = set('xajfb123')
>>> input_set2 = set('122-32+x')
>>> input_set1.issubset(good_set)
False
>>> input_set2.issubset(good_set)
True
>>>