Dan Armentrout <dla0...@uah.edu> added the comment:
Thank you for your quick explanation of this to me. Dan On Tue, Nov 6, 2018 at 8:04 AM Steven D'Aprano <rep...@bugs.python.org> wrote: > > Steven D'Aprano <steve+pyt...@pearwood.info> added the comment: > > This is not a bug, this is standard behaviour, working as designed. > > 'a' is not a copy of the list 'x', 'a' is another name for the same list > as 'x'. Any in-place modifications you make to 'a' happens to the object > itself, the list, which is visible regardless of which name you refer to it > by. > > If you are a C programmer, you can think of this as being similar to > pointers: think of 'x' as a pointer to the list, and 'a' as a pointer to > the same list. (That's more or less what happens under the hood.) From the > Python level, we say that both names 'a' and 'x' refer to the same object. > > If you want a copy, you can use the copy module, or for lists, you can > take a slice: a = x[:] makes a copy of the list. > > For immutable objects like strings, you don't need a copy, because you > cannot modify them in place: any operation on a string always creates a new > string, leaving the old one untouched. > > ---------- > nosy: +steven.daprano > resolution: -> not a bug > stage: -> resolved > status: open -> closed > > _______________________________________ > Python tracker <rep...@bugs.python.org> > <https://bugs.python.org/issue35176> > _______________________________________ > ---------- _______________________________________ Python tracker <rep...@bugs.python.org> <https://bugs.python.org/issue35176> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
