returns 0.3.0

Make your functions return something meaningful and safe!

returns

Make your functions return something meaningful and safe!

Features

• Provides primitives to write declarative business logic
• Fully typed with annotations and checked with mypy, allowing you to write type-safe code as well
• Pythonic and pleasant to write and to read (!)

Installation

pip install returns

What's inside?

We have several the most iconic monads inside:

• Result, Failure, and Success (also known as Either, Left, and Right)
• Maybe, Some, and Nothing

We also care about code readability and developer experience, so we have included some useful features to make your life easier:

• Do notation
• Helper functions

Example

from returns.do_notation import do_notation
from returns.either import Result, Success, Failure

class CreateAccountAndUser(object):
    """Creates new Account-User pair."""

    @do_notation
    def __call__(self, username: str, email: str) -> Result['User', str]:
        """Can return a Success(user) or Failure(str_reason)."""
        user_schema = self._validate_user(username, email).unwrap()
        account = self._create_account(user_schema).unwrap()
        return self._create_user(account)

    # Protected methods
    # ...

We are covering what's going on in this example in the docs.

Inspirations

This module is heavily based on:

• dry-rb/dry-monads
• Ø
• pymonad