simple-result

A very simple, fully typed Rust-like Result type for Python 3.

If you need a Result type only for checking if an operation succeeded or failed, and don't need to perform special actions like chaining operations, mapping, etc., then this library is for you.

If you are looking for a more feature-rich Result type, check out rustedpy/result.

Installation

# Using pip
pip install simple-result

# Using Poetry
poetry add simple-result

# Using uv
uv add simple-result

Usage

import random

from simple_result import Err, Ok, Result

def fetch_data() -> Result[str, ConnectionError]:
    fetched = random.choice([True, False])
    if fetched:
        return Ok('Data fetched!')
    return Err(ConnectionError('Error fetching data!'))

Check if the result is Ok or Err using type narrowing:

if res := fetch_data():
    print(res.value) # "Data fetched!"
    print(res.error) # None
else:
    print(res.error) # "Error fetching data!"
    print(res.value) # None

Or using match:

match fetch_data():
    case Ok(data):
        print(data) # "Data fetched!"
    case Err(error):
        print(error) # "Error fetching data!"

match fetch_data():
    case Ok(data):
        print(data) # "Data fetched!"
    case Err(error, code):
        print(error, code) # "Error fetching data! 1"

Call .unwrap_value() to get the value or raise an UnwrapError if the result is Err:

from simple_result import UnwrapError

try:
    res = Err(ConnectionError('Error fetching data!'))
    print(res.unwrap_value())
except UnwrapError as exc:
    print(str(exc)) # called `Result.unwrap_value()` on an `Err` value
    print(exc.result.error) # "Error fetching data!"

Call .unwrap_error() to get the error or raise an UnwrapError if the result is Ok:

try:
    res = Ok('Data fetched!')
    print(res.unwrap_error())
except UnwrapError as exc:
    print(str(exc)) # called `Result.unwrap_error()` on an `Ok` value
    print(exc.result.value) # "Data fetched!"

Compare results:

assert Ok(1) == Ok(1)
assert Ok(1) != Ok(2)

exc = ValueError('error')
assert Err(exc) == Err(exc)

other_exc = ValueError('other error')
assert Err(exc) != Err(other_exc)

Check if the result is Ok or Err using isinstance:

from simple_result import ResultOption

res = fetch_data()
assert isinstance(res, ResultOption)
assert isinstance(res, (Ok, Err))

Contributing

See the contribution guidelines.

License

This project is licensed under the MIT License. See the LICENSE file for details.

Support

If you find this project useful, give it a ⭐ on GitHub!