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:

Wolfram Research (2015), KeyMemberQ, Wolfram Language function, https://reference.wolfram.com/language/ref/KeyMemberQ.html.

Text

Wolfram Research (2015), KeyMemberQ, Wolfram Language function, https://reference.wolfram.com/language/ref/KeyMemberQ.html.

BibTeX

@misc{reference.wolfram_2021_keymemberq, author="Wolfram Research", title="{KeyMemberQ}", year="2015", howpublished="\url{https://reference.wolfram.com/language/ref/KeyMemberQ.html}", note=[Accessed: 17-October-2021 ]}

BibLaTeX

@online{reference.wolfram_2021_keymemberq, organization={Wolfram Research}, title={KeyMemberQ}, year={2015}, url={https://reference.wolfram.com/language/ref/KeyMemberQ.html}, note=[Accessed: 17-October-2021 ]}

CMS

Wolfram Language. 2015. "KeyMemberQ." Wolfram Language & System Documentation Center. Wolfram Research. https://reference.wolfram.com/language/ref/KeyMemberQ.html.

APA

Wolfram Language. (2015). KeyMemberQ. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/KeyMemberQ.html