KeyFreeQ

KeyFreeQ[assoc,form]

yields True if no key in the association assoc matches form, and yields False otherwise.

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

Examples

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

Wolfram Language code: KeyFreeQ[<|"x" -> 1|>, "x"]

Test whether the association contains a string key:

Wolfram Language code: KeyFreeQ[<|"x" -> 1|>, _String]

KeyFreeQ works with lists of rules:

Wolfram Language code: KeyFreeQ[{a -> 1, b -> 2}, a]

Determine which of the associations does not contain the key:

Wolfram Language code: KeyFreeQ[a] /@ {<|a -> 1|>, <|b -> 2|>}

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