Wolfram: Association. Delete Items by Key

By Xah Lee. Date: . Last updated: .

Delete by Key

KeyDrop
  • KeyDrop[asso, key]
  • KeyDrop[asso, listOfKeys]
  • KeyDrop[listOfAsso, key]

return a new association with some keys removed. (does not modify variable)

KeyDrop 

KeyDrop[ Association[ a -> 1, b -> 2, c -> 3 ], b ]
(* <|a -> 1, c -> 3|> *)
KeyDrop[ Association[ a -> 1, b -> 2, c -> 3 ], {c, b} ]
(* <|a -> 1|> *)
KeyDrop[
{Association[ a -> 1, b -> 2, c -> 3 ],
Association[ a -> 11, b -> 22 ]},
 b ]
(* {<|a -> 1, c -> 3|>, <|a -> 11|>} *)

Association Variable, Delete by Key, Modify Variable

KeyDropFrom[assoVar, key]
  • remove the element with the specified key.
  • modify the variable.
  • return the new value of the variable.

KeyDropFrom 

xx = Association[ a -> 1, b -> 2];

KeyDropFrom[ xx, b ]
(* <|a -> 1|> *)

xx
(* <|a -> 1|> *)
KeyDropFrom[assoVar, listOfKeys]

remove multiple elements. 

xx = Association[ a -> 1, b -> 2, c -> 3, d -> 4];

KeyDropFrom[ xx, {a, c} ]
(* <|b -> 2, d -> 4|> *)

WolframLang, Association (Key Value List)