Python Functional Extensions

This library helps write code in more functional way.

Core Concepts

Get rid of primitive obsession (pydantic compatible)

    first_name = CustomerName.create("")
    second_name = CustomerName.create("John")

    assert first_name.is_failure
    assert first_name.get_error_unsafe == "Invalid name"

    assert second_name.is_success
    assert str(second_name.get_value_unsafe) == "John"

Get rid of the Errors raised and regain control of your flow

    @safe
    def raise_error():
        raise Exception("fatal error")

    result = raise_error()
    assert result.is_failure
    assert result.get_error_unsafe == "fatal error"

Adopt a new development style - Railway programming flavor

    response = get_account(3) \
               | map | account_to_user \
               | map | user_to_account \
               | bind | delete_account \
               | map | increment \
               | bind | get_account \
               | success_unsafe

API Examples

Result

Map

Use case: Transforming the inner value of a successful Result, without needing to check on the success/failure state of the Result

Note: the function (ex create_message) passed to Result.Map() is only executed if the Result was successful

    def create_message(inventory: FruitInventory):
        return f"There are {inventory.count} {inventory.name}(s)"

    apple_inventory = Result.success(FruitInventory("apple", 4))
    banana_inventory = Result.error(Exception("Could not find any bananas"))

    assert apple_inventory.map(create_message) == Result.success("There are 4 apple(s)")
    assert banana_inventory.map(create_message) == Result.error(Exception("Could not find any bananas"))

Example

Read or Watch more about these ideas

Related Projects

• CSharpFunctionalExtensions

Contributors

A big thanks to the project contributors!