WolframLang: Association, Get Value

Get Key's Value

assoc[key]

return the value of a key. Return Missing["KeyAbsent", key] if key no exist. Missing

Lookup[assoc, key]

return the value of key.

If the key no exist, return Missing["KeyAbsent", key].

Lookup

xx = Association[ a -> 3,  b -> 2 ];

Lookup[xx, b] === 2

Lookup[xx, c] === Missing["KeyAbsent", c]

Lookup[assoc, key, default]

gives default if the key no exist.

xx = Association[ a -> 3,  b -> 2 ];

Lookup[xx, c, 99] ===  99

Lookup[assoc, {key1, key2 etc}]

return a list of the values associated with the keys.

Lookup[{assoc1, assoc2 etc}, key]

get a list of values of a key, from the list of associations .