Steven D'Aprano wrote: > On Wed, Dec 09, 2020 at 12:05:17PM -0000, Mathew Elman wrote: > > Steven D'Aprano wrote: > > On Tue, Dec 08, 2020 at 11:46:59AM -0000, Mathew > > Elman wrote: > > I would like to propose adding lazy types for > > casting > > builtins in a > > lazy fashion. e.g. lazy_tuple which creates a reference to the > > source iterable and a morally immutable sequence but only populates > > the tupular container when it or the source is used. > > What are your use-cases for this? > > Does this include things like lazy_list, lazy_float, > > lazy_bool, > > lazy_str, lazy_bytearray etc? > > I would say yes, it should include these types as well. > > The use case is for when you are casting between types a high number > > of times to pass them around, especially into another type and back. > > I would say, don't do that. If you have a list, and you pass it to > another function after converting to a tuple, why would you take that > tuple and convert back to a list when you already have a list? > For types like casting back and forth between float and int, there will > be data loss. > Even if there is not, the overhead of creating a "lazy proxy" to the > float is probably greater than just converting. I see what you mean here, I think my initial thought was more towards container types rather than ints and floats, I said these should be included because I saw no reason why not. Thinking about it, for int and float types it makes less sense, because you have no great saving, whereas for a container type, you can increase the reference count by 1 instead of N.
> > How do these > > hooks freeze the list? > > they don't freeze the list, they freeze the values in the lazy_tuple > > when the list is mutated, so when mutating the list, the values in the > > tuple are set (if they have not been already), so that they aren't > > also mutated in the lazy_tuple. You seem to be referring to the lazy_tuple as the hook, I am saying that _I_ could implement a lazy class if hooks existed. i.e. I could make a class `LazyTuple` that when instanced with a list, creates and stores the hooks on itself. > > How is this supposed to work in practice? A method e.g. `create_hook(method, callback)` would return a concrete reference to the hook, and uses a weak reference to know if it needs to execute the callback (meaning that it would only add the overhead of a check for callbacks if the concrete reference still existed). > > Where does the hook live? When > is it called? What does it do? > How does the lazy tuple know that the list's setitem has been called? It knows because of a hook? This is my whole point about including hooks in this thread, i.e. if it was possible to add a callback on a method, it would execute when it is called. I am not sure I understand your question. _______________________________________________ Python-ideas mailing list -- python-ideas@python.org To unsubscribe send an email to python-ideas-le...@python.org https://mail.python.org/mailman3/lists/python-ideas.python.org/ Message archived at https://mail.python.org/archives/list/python-ideas@python.org/message/GD3TTQPULXGVQIKQUTERF6MAOD5WUS4B/ Code of Conduct: http://python.org/psf/codeofconduct/
