Wolfram Language & System 10.3 (2015)|Legacy Documentation

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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.

ExamplesExamplesopen allclose all

Basic Examples  (4)Basic Examples  (4)

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

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Test whether the association contains a string key:

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KeyMemberQ works with lists of rules:

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Determine which of the associations does not contain the key:

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Introduced in 2015
(10.3)