ResultWrapper

How to install it?

You can install ResultWrapper from this Github repository with python3 setup.py install, or just install it directly from pypi with pip3 install result-wrapper.

What is it?

ResultWrapper is a very small utility library that provides a class containing either an Error, or a set of Results. This can be used in APIs to quickly and easy communicate if the operation failed or not. A ResultWrapper instance provides access to its underlying results if it did not fail, otherwise all access to possible results are denied.

How to use it?

To enable the capabilities of ResultWrapper, decorate a function with the wrap_result decorator. This function then returns an instance of ResultWrapper. To check wether a ResultWrapper is failed or not, use the .failed property.

You can pass a tuple of exception classes that should be caught and transformed to a failed Result in the decorator parameter exceptions:

from result_wrapper import wrap_result

@wrap_result(exceptions=(ValueError,))
def function1():
    raise ValueError("This exception will be caught and transformed to a failed result.")

@wrap_result(exceptions=(ValueError,))
def function2():
    raise TypeError("This exception will not be caught. The exception is thrown normally.")

assert function1().failed is True
function2() # this will throw TypeError !!!

Another way of returning a failed result is to use the ResultWrapper.make_failed function:

from result_wrapper import wrap_result, ResultWrapper

@wrap_result
def function1():
    return ResultWrapper.make_failed()

assert function1().failed is True

Optionally you can pass any object to the make_failed function to pass some error information to the caller. In the case of a thrown exception, the error information is set to the arguments to the constructor of the exception:

from result_wrapper import wrap_result, ResultWrapper

@wrap_result
def function1():
    return ResultWrapper.make_failed({"ErrorID": 1})

@wrap_result(exceptions=(ValueError,))
def function2():
    raise ValueError({"ErrorID": 1})

assert function1().error_information.get("ErrorID") == 1
assert function2().error_information.get("ErrorID") == 1

To return a successful result, return an instance of Result or ResultWrapper.make_succeeded:

from result_wrapper import wrap_result, Result, ResultWrapper

@wrap_result
def function1():
    return Result(result1="value1", result2=2)

@wrap_result
def function2():
    return ResultWrapper.make_succeeded(result1="value1", result2=2)

result = function1()
assert result.result1 == "value1"
assert result.result2 == 2

result = function2()
assert result.result1 == "value1"
assert result.result2 == 2