Chained assignment and mutation

Question

Accepted Answer

Chained assignment 'a = b = []' creates one list and binds both names to it - it does not create two separate empty lists. Every mutation through either name changes the same object, so after both appends a is [1, 2] and a is b is True. To get two independent lists, write a = []; b = []. This is the same reference-semantics rule that applies to all Python assignment.