20.07.17 04:35, Alexander Belopolsky пише:
On Wed, Jul 19, 2017 at 9:08 PM, Guido van Rossum <guido@python.org> wrote:
The proposal in your email seems incomplete
The proposal does not say anything about type((x=1, y=2)). I assume it will be the same as the type currently returned by namedtuple(?, 'x y'), but will these types be cached? Will type((x=1, y=2)) is type((x=3, y=4)) be True?.
Yes, this is the key problem with this idea. If the type of every namedtuple literal is unique, this is a waste of memory and CPU time. Creating a new type is much more slower than instantiating it, even without compiling. If support the global cache of types, we have problems with mutability and life time. If types are mutable (namedtuple classes are), setting the __doc__ or __name__ attributes of type((x=1, y=2)) will affect type((x=3, y=4)). How to create two different named tuple types with different names and docstrings? In Python 2 all types are immortal, in python 3 they can be collected as ordinary objects, and you can create types dynamically without a fear of spent too much memory. If types are cached, we should take care about collecting unused types, this will significantly complicate the implementation.