How do I use the constructor of a python Generic typed class?
T = typing.TypeVar('T')
class MyClass(typing.Generic[T]):
def __init__(self, initialValue: typing.Iterable):
self.values: T = T(initialValue)
test = MyClass[tuple[int]]([1, 2, 3])
In this case I am expecting T(initialValue) to be equivalent to tuple(initialValue) but instead I get an error. "Exception has occurred: TypeError 'TypeVar' object is not callable"
I guess that's not too surprising since that's not what typing was built for, but is there a workaround to accomplish this?
You'll need to take an explicit factory method. Type annotations only exist for compile-time purposes, and at runtime that T is just a TypeVar. Consider
class MyClass(Generic[T]):
def __init__(self, initialValue: Iterable[int], factory: Callable[[Iterable[int]], T]):
self.values: T = factory(initialValue)
Then call it as
test = MyClass([1, 2, 3], lambda x: tuple(x))
Note: It would be nice to just pass tuple as the second argument, but mypy seems to choke when converting that typename to a Callable. Other type checkers may be able to handle it; your mileage may vary.
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