katharos 1.0.0

A functional programming library for Python that provides algebraic abstractions like Semigroups, Monoids, Functors, Applicatives, and Monads, along with immutable data structures to enable composable, type-safe, and side-effect-free code.

Katharos

Functional programming abstractions for Python — Monads, Applicatives, Functors, and immutable data structures for composable, type-safe code.

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Installation

pip install katharos

Quick Start

Handle optional values without None checks:

from katharos.types import Maybe

result = Maybe.Just(5) | (lambda x: Maybe.Just(x * 2))  # Just(10)
nothing = Maybe.Nothing() | (lambda x: Maybe.Just(x * 2))  # Nothing()

Model errors as values instead of exceptions:

from katharos.types import Result

def parse_int(s: str) -> Result[ValueError, int]:
    try:
        return Result.Success(int(s))
    except ValueError as e:
        return Result.Failure(e)

parse_int("42") | (lambda n: Result.Success(n * 2))  # Success(84)
parse_int("??") | (lambda n: Result.Success(n * 2))  # Failure(...)

Chain operations with do-notation:

from katharos.types import Maybe
from katharos.syntax_sugar import do, DoBlock

@do(Maybe)
def lookup_discount(user_id: int) -> DoBlock[float]:
    user    = yield find_user(user_id)      # short-circuits on Nothing
    account = yield find_account(user)
    return account.discount

lookup_discount(42)  # Just(0.15) or Nothing()

Combine values with the Semigroup operator:

from katharos.types import ImmutableList

ImmutableList([1, 2]) @ ImmutableList([3, 4])  # ImmutableList([1, 2, 3, 4])

Documentation

Full tutorials, how-to guides, API reference, and explanations of the mathematical foundations are at katharos.readthedocs.io.

License

MIT