Also, strictly speaking, Python is not "pass by reference" as the term is used for other languages. It's more accurately "pass by object" or "pass by object reference." Somewhat of a pedantic distinction, and the quiz question is clear regardless.

[1] http://robertheaton.com/2014/02/09/pythons-pass-by-object-re...

[2] http://foobarnbaz.com/2012/07/08/understanding-python-variab...

[3] https://jeffknupp.com/blog/2012/11/13/is-python-callbyvalue-...