For me the feeling is that the ? denotes better optional, ~int to me feels more like not int... than int or None :-) On Fri, Sep 20, 2019 at 10:19 AM Philippe Prados <philippe.prados@gmail.com> wrote:
Hello everybody,
I just publish the PEP-0604 <https://www.python.org/dev/peps/pep-0604/> for discussions (https://www.python.org/dev/peps/pep-0604/).
Scala 3 propose a new syntax for Union type. See here <https://dotty.epfl.ch/docs/reference/new-types/union-types.html>. I propose to add a similar syntax in Python.
# Operator for Union assert( int | str == Union[int,str]) assert( int | str | float == Union[int,str,float]) # Operator for Optional assert( ~int == Optional[int])
Now, it's possible to write:
def fn(bag:List[int | str], option: ~int = None) -> float | str: ...
in place of
def fn(bag:List[Option[int,str]], option: Optional[int] = None) -> Union[float,str]: ...
The discussion on python-new@python.org here <https://mail.python.org/archives/list/python-ideas@python.org/thread/FCTXGDT...> have emerged the idea of extending also issubclass() and isinstance().
isinstance(int, int | str)
I think these syntaxes are more clear, and can help with the adoption of typing.
I test and implement these ideas in a two fork : One for CPython <https://github.com/pprados/cpython/tree/updage_isinstance> and one for MyPy <https://github.com/pprados/mypy/tree/add_INVERT_to_types>. See the branches add_OR_to_types (for Union syntax), add_INVERT_to_types (for Union and Optional syntax) or updage_isinstance (for new isinstance() and issubclass()).
How I implement that ? I add the operators __or__ and __revert__ to PyType_Type. The C code is similar of :
from typing import * def type_or(self,right): return Union[self,right] type(type).__or__ = type_or
with some check before return Union.
Actually, the accepted BNF syntax for typing is :
annotation: name_type name_type: NAME (args)? args: '[' paramslist ']' paramslist: annotation (',' annotation)* [',']
I propose to extend the BNF syntax to :
annotation: ( name_type | or_type | invert_type ) name_type: NAME (args)? args: '[' paramslist ']' paramslist: annotation (',' annotation)* [',']
or_type: name_type '|' annotation
invert_type: '~' annotation
Your remarks are welcome. Philippe Prados _______________________________________________ Typing-sig mailing list -- typing-sig@python.org To unsubscribe send an email to typing-sig-leave@python.org https://mail.python.org/mailman3/lists/typing-sig.python.org/