fetch annotations defined in __init__

sample.py

import ast
import inspect


class InitAnnotations(ast.NodeVisitor):
    def __init__(self, locals_, globals_):
        self.globals = globals_
        self.locals = locals_
        self.annotations = {}

    def visit_AnnAssign(self, node: ast.AnnAssign):
        if not node.simple:
            if isinstance(node.annotation, ast.Constant):
                annotation = node.annotation.value
            else:
                annotation = node.annotation.id
            self.annotations[f"self.{node.target.attr}"] = eval(
                annotation,
                self.globals,
                self.locals
            )


def get_init_annotations(cls: type) -> dict[str, type]:
    try:
        src = inspect.getsource(cls)
    except OSError:
        print("cheeky, huh? 😒")
        return {}
    anno = InitAnnotations(vars(cls), vars(inspect.getmodule(cls)))
    anno.visit(ast.parse(src))
    return anno.annotations


class Foo:
    class Bar:
        pass
    def __init__(self):
        i: int = 1
        self.x: int = 3
        if False:
            self.y: str = "still a valid annotation"
        self.z: Bar = Bar()
        self.a: "Foo" = self


print(get_init_annotations(Foo))
# {'self.x': <class 'int'>, 'self.y': <class 'str'>, 'self.z': <class '__main__.Foo.Bar'>, 'self.a': <class '__main__.Foo'>}