On Mon, 19 Feb 2018 04:26:32 +0100, Anders Wegge Keller wrote: > På Mon, 19 Feb 2018 08:47:14 +1100 > Tim Delaney <timothy.c.dela...@gmail.com> skrev: >> On 18 February 2018 at 22:55, Anders Wegge Keller <we...@wegge.dk> >> wrote: > > >> > That list is not only weakly typed, but rather untyped. There are no >> > safeguards in the language, that enforce that all elements in a list >> > or other container are in fact of the same type. Before type >> > annotations and mypy, I could not enforce that other than at runtime. > >> You couldn't have got the above much more wrong. > >> As others have said, typing is about how the underlying memory is >> treated. > > And that is exactly my point. Python does not have a typed list. It > have a list that takes whatever is thrown into it. > > I'll skip the rest, as you totally missed the point.
I think its actually you have totally missed the point. What you want is a homogeneous list, a list which only accepts items of the same type. The built-in list is not that data structure, but Python already has something similar: see the array module. If you want a list type which only supports items of a single type, you can get one by subclassing. But that's utterly irrelevant to the question of strong versus weak typing. A strongly typed language like Haskell, which does (almost?) no automatic coercions at all (possibly not even int to float) can still define a "list of Any object" type, just like Python's built-in list. That doesn't make Haskell untyped, and it is a sign of your confusion that you think it makes Python untyped. Sorry to be blunt, but you're not even in the right ballpark here. Python is strongly typed because a list is a list, regardless of its contents. If you say "1 + []" Python does not try to cast or convert the list into an int and add them, or interpret the int as a list, and perform list concatenation on a chunk of memory that is actually an int but is being treated as an (almost certainly invalid!) list. Remember: - the static/dynamic distinction is between *when* types are checked (compile time or run time), not *whether* they are checked; - untyped languages treat *everything* (or almost everything) as the same type: usually either a chunk of raw bits, like in assembly, or text strings, like in many shell scripting languages; - weakly typed languages do a lot of automatic coercions; - strongly typed languages do very few or no automatic coercions. None of those distinctions have anything to say about whether the standard library offers a homogeneous list where all the items have the same type. -- Steve -- https://mail.python.org/mailman/listinfo/python-list
