Rust Result for Python

rust_result_for_python.py

import sys
import traceback


class CallableResult:
    class NoneResult:
        pass

    NONE = NoneResult

    def __init__(self):
        self.value = self.NONE
        self.exception = None
        self.traceback = None

    def __call__(self, func):
        def wrapper(*args, **kwargs):
            try:
                self.value = func(*args, **kwargs)
            except Exception as err:
                self.exception = err
                contents = traceback.format_exception(*sys.exc_info())
                self.traceback = ''.join(contents)
            return self
        return wrapper

    def __bool__(self):
        return self.value != self.NONE


def Result(func):
    return CallableResult()(func)


@Result
def foo():
    raise ValueError("error in foo")


@Result
def bar(x, y):
    return x + y


result1 = foo()
if not result1:
    # do something
    print(result1.traceback)
else:
    print(result1.value)


result2 = bar(2, 5)
if not result2:
    # do something
    print(result2.traceback)
else:
    print(result2.value)