KeyMemberQ

KeyMemberQ[assoc,form]

yields True if a key in the association assoc matches form, and False otherwise.

KeyMemberQ[form]

represents an operator form of KeyMemberQ that can be applied to an expression.

Examples

Basic Examples  (4)

Test whether "x" is a key in the association:

Test whether the association contains a string key:

KeyMemberQ works with lists of rules:

Determine which of the associations does not contain the key:

Introduced in 2015
 (10.3)