haskellian 0.5.1

The functional programming library you need

Haskellian

The python functional programming library you need

pip install haskellian

Why

• Lazy imports + stub files -> great linting and 0 import time (thanks to lazy-loader)
• Monadic, method chaining style
• Great typing and overloads

Classes

Iter[A]

from haskellian import Iter, iter as I

@I.lift
def gen():
  for i in range(100000000000):
    yield i

gen() \
  .map(lambda x: 2*x) \
  .filter(lambda x: x % 2 == 0) \
  .batch(2) \
  .skip(1)
  #.sync() # don't recommend it...

# Iter([(4, 6), (8, 10), (12, 14), (16, 18), (20, 22), ...])

Either[L, R]

def fetch_users() -> Either[str, list[str]]:
  ...

def fetch_user(id: str) -> Either[str, dict]:
  ...

def parse_user(user: dict) -> Either[str, User]:
  ...

@E.do()
def print_one():
  users = fetch_users().unsafe()
  raw_user = fetch_user(users[0]).unsafe()
  user = parse_user(raw_user).unsafe()
  print(user)

Explanation:

• .unsafe() raises unwraps the value or raises an IsLeft exception
• @E.do() wraps the function in a try...except IsLeft block, returning the possibly raised Left

Dict[A]

from haskellian import Dict

Dict({ 'a': 1, 'b': 2, 'c': 4 }) \
  .filter_v(lambda v: v % 2 == 0) \
  .evolve({ 'c': lambda x: -x })
  .map_v(lambda v: 2*v)

# Dict({ 'b': 4, 'c': -8 })

AsynIter[A]

from haskellian import AsynIter, asyn_iter as AI

@AI.lift
async def gen():
  for i in range(10):
    yield i

await gen() \
  .map(lambda x: 2*x) \
  .filter(lambda x: x % 2 == 0) \
  .batch(2) \
  .skip(1) \
  .sync()