So my problem is the following

from typing import ClassVar, TypeVar

from hypothesis import strategies as st

T = TypeVar("T", bound="FixedUint")


class FixedUint(int):
    MAX_VALUE: ClassVar["FixedUint"]

    def __init__(self: T, value: int) -> None:
        if not isinstance(value, int):
            raise TypeError()

        if value < 0 or value > self.MAX_VALUE:
            raise OverflowError()


class U256(FixedUint):
    pass


U256.MAX_VALUE = int.__new__(U256, (2**256) - 1)


class U64(FixedUint):
    pass


U64.MAX_VALUE = int.__new__(U64, (2**64) - 1)



st.from_type(U64).example()
# TypeError: 'value' is an invalid keyword argument for int()

ie that hypothesis cannot build from type because the __init__ of FixedUint has a value kwarg for validation, but U64(value=1234) is actually not valid.

How to make this work?

So my problem is the following

from typing import ClassVar, TypeVar

from hypothesis import strategies as st

T = TypeVar("T", bound="FixedUint")


class FixedUint(int):
    MAX_VALUE: ClassVar["FixedUint"]

    def __init__(self: T, value: int) -> None:
        if not isinstance(value, int):
            raise TypeError()

        if value < 0 or value > self.MAX_VALUE:
            raise OverflowError()


class U256(FixedUint):
    pass


U256.MAX_VALUE = int.__new__(U256, (2**256) - 1)


class U64(FixedUint):
    pass


U64.MAX_VALUE = int.__new__(U64, (2**64) - 1)



st.from_type(U64).example()
# TypeError: 'value' is an invalid keyword argument for int()

ie that hypothesis cannot build from type because the __init__ of FixedUint has a value kwarg for validation, but U64(value=1234) is actually not valid.

How to make this work?

• python
• python-hypothesis

1 Answer 1

It turned out that we needed some small changes, which have been released as Hypothesis 6.123.0; once you update to that version the complete fix is to make all arguments to __init__ positional-only, i.e.

    def __init__(self: T, value: int, /) -> None:
    #                               ^^^
    #                               add this bit