Magnus Lycka wrote: > Ed Singleton wrote: > >> The point is that having to use del to clear a list appears to the >> inexperienced as being an odd shaped brick when they've already used >> the .clear() brick in other places. > > > Agreed. The smart way to go from this stage of surprise is > not to assume that Python is broken, but to try to understand > how lists are different from e.g. dicts, and why the so-much- > smarter-than-me Python designers made it like this.
That two of Python's three built-in mutable collections support clear() is clearly a historical artifact. > Not that Python is perfect, but when you don't get a > "sorry, this change would break existing code, won't happen > until Python 3.0"-resonse, but a "study this more"-response, > the smart thing is to open your mind and try to fully grok > this. The original question was about idioms and understanding, but there's more to the case for list.clear. Python is "duck typed". Consistency is the key to polymorphism: type X will work as an actual parameter if and only if X has the required methods and they do the expected things. Emptying out a collection is logically the same thing whether that collection is a list, set, dictionary, or user-defined SortedBag. When different types can support the same operation, they should also support the same interface. That's what enables polymorphism. -- --Bryan -- http://mail.python.org/mailman/listinfo/python-list
