On Fri, Oct 12, 2018 at 9:16 AM Steven D'Aprano <steve@pearwood.info> wrote:
On Fri, Oct 12, 2018 at 02:45:30AM +1100, Chris Angelico wrote:
On Fri, Oct 12, 2018 at 2:41 AM Chris Barker - NOAA Federal via Python-ideas <python-ideas@python.org> wrote:
This violates the Liskov Substitution Principle.
If we REALLY had a time machine, then dict would subclass frozendict, and we’d be all set.
Thanks to virtual subclassing, we can still do this. The question is, should we?
Intuition tells me that a frozen dictionary is a form of dictionary that adds restrictions, not that a dictionary is a frozen dictionary that you left out to thaw.
No offence Chris, but that's why we shouldn't program by intuition :-)
But as we see from [frozen]set, it's probably best to treat them as completely independent classes, both implementing the basic Mapping interface.
Indeed.
Which was my point. They probably should NOT be in a direct hierarchy, partly because people's intuition WILL lead them to a dangerous expectation. ChrisA