R. David Murray added the comment: Yep, this is the way it works. When a class attribute name is referenced on an instance object, you are referencing the object pointed to by the class name. What happens next depends on what kind of object you have, and what kind of operation you perform. In this case, you have an immutable object, and the addition operation returns a new immutable object, which gets assigned (as always happens) to the instance attribute name. If tot was, say, [0] and the operation was self.tot += [1], your print would print [0, 1] [0, 1], because the in-place addition operation on lists *mutatates* the list, and what gets assigned to the instance attribute name is a pointer to the *same* object that the class attribute points to.
In short, this is a more subtle instance of the confusion discussed here: https://docs.python.org/3/faq/programming.html#why-did-changing-list-y-also-change-list-x (and also the FAQ that follows that one). ---------- nosy: +r.david.murray resolution: -> not a bug stage: -> resolved status: open -> closed _______________________________________ Python tracker <rep...@bugs.python.org> <http://bugs.python.org/issue23824> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
