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KeyExistsQ

KeyExistsQ

KeyExistsQ[assoc,key]

returns True if the specified key exists in the association assoc, and False otherwise.

KeyExistsQ[key]

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

Details

KeyExistsQ can be applied not only to Association objects, but also to lists of rules.
KeyExistsQ[key][expr] is equivalent to KeyExistsQ[expr,key].

Examples

Basic Examples (2)

Test if a key exists in an association:

Test if a key exists in a list of rules:

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