In python, is there a way to exit a class after testing a condition, without exiting out of python?

say i have the class

class test():
     def __init__(self):
         self.a = 2

     def create_b(self):
         self.b = 3

     def does_b_exist(self):
         if <self.b doesnt exist>:
             #terminate

         self.b += 1

try/except` doesnt work since the rest of the program doesnt terminate after failing. im basically trying to catch an error, and do what python does when it shows you errors, but i cant figure out how to do it