On 09/10/2015 17:26, John Michael Lafayette wrote:
I would like Python to have a strong typing feature that can co-exist
with the current dynamic typing system. Currently Python is like this:
var animal = Factory.make("dog") # okay.
var dog = Factory.make("dog") # okay.
var cat = Factory.make("dog") # are you sure?
AFAIK (I'm not an expert) that isn't Python. And you wouldn't expect
Python to know about the names of animals and their relationships to
each other so that it can give that sort of warning.
I would like Python to also be able to also do this:
Animal a = Factory.make("dog") # okay. Dog is Animal.
Dog d = Factory.make("dog") # okay. Dog is Dog.
Cat c = Factory.make("cat") # Runtime error. Dog is not Cat.
It seems you're looking for a radically different language (statically
typed amongst other things).
But I think you can define Animal, Dog and Cat such that you can write this:
a = Factory.make(Animal,"dog")
d = Factory.make(Dog,"dog")
c = Factory.make(Cat,"cat")
and program it so that it behaves the way you want. That doesn't need
any language changes.
With a strong typing option that performs runtime type checking, the
reader can be certain that the program is running the type they expect.
Also, the IDE can be more helpful. Example:
var dog = Factory.make("dog") # okay
dog. (Ctr+Space) # Auto-complete lists only
Animal methods.
Even as a non-expert, I know that is not possible unless it is
completely transformed (or you are running it interactively).
Neither the IDE nor the Python bytecode compile can know what Factory or
make are going to be until runtime, and even then, not until it's about
to execute that line (and perhaps not even by that point sometimes, if
the evaluation of the line can change the meaning of Factory).
This feature can be completely optional and could be integrated without
anyone noticing. If it is integrated, only the people who want this type
safety would have to use it. If there is a performance penalty, it would
mainly affect the people who use this feature. Given that a lot of
people transition from C/C++/Java to Python, I think that this feature
would be intuitive to many users and a good addition for people who like
type safety.
Remember that Python allows this:
if randombit(): # 1 or 0
import A
else:
import B
A defines Factory as that complex class or whatever you had in mind.
While B defines Factory as:
Factory = 42
--
bartc
--
https://mail.python.org/mailman/listinfo/python-list
