ArrayRules

ArrayRules[SparseArray[...]] gives the rules {pos1 -> val1, pos2 -> val2, ...} specifying elements in a sparse array.

ArrayRules[list] gives rules for SparseArray[list].

Examples

Get rules from a sparse array:

sa = SparseArray[{{1, 2} -> 1, {2, 1} -> 2}];
ArrayRules[sa]
(* {{1, 2} -> 1, {2, 1} -> 2, {_, _} -> 0} *)

Convert a list to sparse array rules:

ArrayRules[{{1, 0}, {0, 2}}]

Please visit the official Wolfram Language Reference for more details.