NotIn
NotIn is a concept used in programming to denote that an element is not a member of a collection. It appears as an operator or function in several languages, often written as not in or as a negated in clause.
In Python, the dedicated operator not in tests membership: x not in y evaluates to True when
In SQL, NOT IN filters rows whose value does not match any value in a list or
In Kotlin and some other languages, the negated form is built from in and !in: a !in
NotIn semantics and performance vary by language. As a general rule, membership tests are faster for hash-based