Zac-HD / monad

Playing with result types in Python

Monadic Control in Python

This is an experimental module for playing with the result monad in Python, which interfaces fairly nicely with exceptions.

It is inspired by Rust's Result type and pattern-matching. If you want to use something like this in your own code, the [monad](https://github.com/pyx/monad) or [oslash](https://github.com/dbrattli/OSlash) packages on pypi might be a better choice.

As well as checking the res.ok and res.err values, you can res.unwrap() - which raises the err exception or returns the ok value. It's also safe to use Result.unwrap on any other value - it will be returned unchanged.

You can apply a series of functions with res.then(func1).then(func2). You can even decorate your own functions with @Result.decorate to transform any return value or thrown exception into a result value.

Here's some examples:

>>> from result import Result
    Result(1).then(lambda x: x + 1).then(lambda x: x ** 2)
Result(ok=4)

>>> Result([1, 2, 3]).then(lambda x: x[4])
Result(err=list index out of range)

>>> Result(1).unwrap() == Result.unwrap(1) == 1
True

>>> @Result.decorate
    def my_func(x):
        return 1 / x

    my_func(2)
Result(ok=0.5)

>>> my_func(0)
Result(err=division by zero)

Comments on ergonomics or edge cases welcome.