The except clause in Python is used to catch specific exceptions. In this case, you are using ButtError in the except clause, which is not a built-in or existing error type. However, this does not cause a NameError immediately because Python does not evaluate the name of the exception (e.g., ButtError) unless the exception is actually raised. The code runs up until an exception is triggered, and only then does Python check whether the exception being raised matches any of the except clauses.