Algebraic effects in Python?

Python Help
1

I’m trying to map out what’s already been done with algebraic effects / effect handlers in Python, and I’d love pointers from people who know the space.

I’m aware generators (yield / send) and context managers can approximate one-shot, shallow handlers, but I’m more interested in fuller or more principled attempts — libraries, research experiments, or write-ups.

A few things I’m specifically curious about:

  • libraries that implement effects as a first-class abstraction
  • anything that tackles multi-shot continuations (greenlets? CPS transforms?)
  • how these compare to handlers in Koka / Eff / OCaml

Pointers, war stories, or “don’t bother, here’s why” all welcome.

2

I had to look that up. Thanks for the opportunity to learn.

On PyPI, some matches exist that you may want to explore: simple-eff and eff. Looking at their release history, the topic seems far from mainstream.

3

Most likely, some of the concepts you’re looking for are hard to even define (at least in a meaningful way) for Python, because the language is fundamentally so different from ones designed to focus purely on the functional paradigm.

4

Thanks for the replies! I eventually came across this:

I tried a small example that explores both states of a feature flag:

from aleff import create_handler, effect

feature_enabled = effect("feature_enabled")

def checkout_total():
    shipping = 0 if feature_enabled("free_shipping") else 500
    return 3_000 + shipping

explore_both = create_handler(feature_enabled)

@explore_both.on(feature_enabled)
def _(resume, flag):
    return {"off": resume(False), "on": resume(True)}

print(explore_both(checkout_total))
# {'off': 3500, 'on': 3000}

This is the kind of multi-shot behavior I was looking for. Thanks again!