This programming language misconception is about the meaning of Python's = operator.

Incorrect and Correct Conception

Convince Yourself

You see that the assignment to b[1] modified the list b refers to, but also the list a refers to!

print(a is b)

The behavior occurs because a and b refer to the same list. The variable a contains a reference to the list, and the assignment copied that reference into the variable b.

Learn More

If you would like to learn more about this misconception, including its possible origins, symptoms students who hold this misconception might exhibit, the related programming language concepts, links to the corresponding parts of the Python language specification, and related misconceptions, check out AssignmentCopiesObject in the progmiscon.org misconception inventory.