pycroscope.runtime

Expose an interface for a runtime type checker.

pycroscope.runtime.is_assignable(value: object, typ: object) → bool

Return whether value is assignable to typ.

This is essentially a more powerful version of isinstance(). Examples:

>>> is_assignable(42, list[int])
False
>>> is_assignable([], list[int])
True
>>> is_assignable(["x"], list[int])
False

The term “assignable” is defined in the typing specification:

https://typing.readthedocs.io/en/latest/spec/glossary.html#term-assignable

pycroscope.runtime.get_assignability_error(value: object, typ: object) → str | None

Return an error message explaining why value is not assignable to type, or None if it is assignable.

Examples:

>>> print(get_assignability_error(42, list[int]))
Cannot assign Literal[42] to list

>>> print(get_assignability_error([], list[int]))
None
>>> print(get_assignability_error(["x"], list[int]))
In element 0
  Cannot assign Literal['x'] to int

pycroscope.runtime.is_compatible(value: object, typ: object) → bool

Deprecated alias for is_assignable(). Use that instead.

pycroscope.runtime.get_compatibility_error(value: object, typ: object) → str | None

Deprecated alias for get_assignability_error(). Use that instead.