Rsult

Rsult (rust result = rs + result) is a python library for adding rust like Result[T, E] support to python.

Background

In rust, rather than throw exceptions up some side channel, you return them directly as part of a functions response. These responses are wrapped in what rust refers to as a Result. Result's are simple objects which contain either the result of the function call, or an exception which was raised by the function.

Usage

There are many ways you can choose to use the rsult Result class. The most common use is to just unpack the response into individual error and response variables. However, the unwrap() functio can also be used much like unwrap in rust. When called from a result that does not contain an error, unwrap(result) will return the response from the function. If unwrap(result) is called with a result that contains an error, that error will be raised as an exception.

Examples

from rsult import Result, unwrap, wrap, wrap_error

class LessThanZeroError(Exception):
    pass

def add_numbers(x: int, y: int) -> Result[int, LessThanZeroError]:
    z = x + y
    if z < 0:
        return wrap_error(LessThanZeroError())
    return wrap(z)

# a regular call to the function that returns the response
error, answer = add_numbers(2, 2)
assert error is None
assert answer == 4

# a call to the function that results in an error
error, answer = add_numbers(2, -4)
assert type(error) is LessThanZeroError
assert answer is None

# unwrap can be used to throw the error, rather than unpacking the result
result = add_numbers(2, -4)
answer = unwrap(result)  # <-- LessThanZeroError gets throw

Authors

• PattyC (schlerp)