[docs] [issue23406] interning and list comprehension leads to unexpected behavior

R. David Murray report at bugs.python.org
Fri Sep 4 16:23:13 CEST 2015

R. David Murray added the comment:

What is actually happening is that the *contents* of the list are copied, but the list itself is not.  This is a consequence of the definition in terms of +.  So, yes, that is a shallow copy, but not quite in the sense that mylist.copy() is a shallow copy, since the references to the contents of s get appended to the list being constructed by *, not a new list that is a "copy" of s.

You are correct that "s is only referenced" is not really accurate.  But how about "Note that the contents of the *s* object are not copied, they are referenced multiple times".  I think that highlights the source of the confusion: that the *contents* are not copied.


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