forechan 0.2.10

Go style CSP for Python

Forechan

go style asyncio channels.

Fully Typed with Generics, mypy ready.

Inspired by core.async from clojure.

Examples

Send & Recv

ch = chan(int)         # Chan[int]
await (ch << 2)        # or use `await ch.send(x)`
two = await ([] << ch) # or use `await ch.recv()`
assert two == 2

# `ch.close()` is idempotent
await ch.close()

Basic

if ch:
  # if `Chan[T]` is open

len(ch) # How many items are in `ch`

async with ch:
  # close `ch` after exiting lexical-scope

async for item in ch:
  # use `ch` as AsyncIterator

Select

async for ch, item in select(ch1, ch2, ch3, ...):
  if ch == ch1:
    ...
  elif ch == ch2:
    ...
  elif ch == ch3:
    ...

Wait Group

wg = wait_group()

for _ in range(5):
  async def cont() -> None:
    with wg:
      # do some work

  create_task(cont())

# will wait for all work to be completed
await wg.wait()

Synchronous

head = ch.try_peek() # can throw `ChanEmpty`
(ch < 2)             # or use `ch.try_send(2)` , can throw `ChanFull`
two = ([] < ch)      # or use `ch.try_recv()`  , can throw `ChanEmpty`
assert two == 2

Go -> Python

The following are roughly equivalent

func fn() {
	// do things here
}
go fn()

When GOMAXPROCS=1

async def fn() -> None:
  # do things here

create_task(fn())

Common Concurrency Patterns

Consumer

async def consumer() -> None:
  async for item in ch:
    # do something with `item`, until `ch` is closed

Producer

def producer() -> Chan[int]:
  ch = chan(int)

  async def cont() -> None:
    # auto close `ch` when done
    async with ch:
      while ...:
        # send result `item` to downstream `ch`
        await (ch << item)

  create_task(cont())
  return ch

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