using vtypes with a run-time type checker

[piccolbo]

I was wondering if it would be possible to use vtypes as type hints and have them checked at run-time. I tried in combination with pytypes and it doesn't work, meaning that one can't pass an int > 0 as a PositiveInt. It will still fail.

from vtypes import vtype
from pytypes import typechecked

PositiveInt = vtype('PositiveInt', int, {'should be positive': lambda x: x >= 0})

assert isinstance(2, PositiveInt)
@typechecked
def f(x: PositiveInt):
    return x
print(f(2))

output:

Traceback (most recent call last):
  File "/Users/antonio/Projects/own/ascetiprogrammer/snippets/sketch.py", line 11, in <module>
    print(f(2))
pytypes.exceptions.InputTypeError: 
  __main__.f
  called with incompatible types:
Expected: Tuple[PositiveInt]
Received: Tuple[int]

Hence the assertion passes, but pytpes doesn't accept 2 as a PositiveInt. I looked at the code and it is using an internal _isinstance rather than the built in isistance.

The goal would be to be able to write something like

@stricttypes # fantasy decorator
def sqrt(x: PositiveInt): #or PositiveNumber
   ....

Thanks!

[smarie]

Good catch @piccolbo ! Indeed this is a known issue in pytypes, that I reported some time ago : Stewori/pytypes#86

[piccolbo]

OK will follow there.