Your First Program

Let's build a simple producer-consumer example using pychanio.

import asyncio
from pychanio import chan, go, close

async def producer(ch):
    for i in range(3):
        msg = f"msg-{i}"
        print(f"Producing: {msg}")
        ch << msg  # async send
        await asyncio.sleep(0.2)
    close(ch)  # close the channel

async def consumer(ch):
    async for msg in ch:
        print(f"Consumed: {msg}")

async def main():
    ch = chan()
    go(producer, ch)
    await consumer(ch)

if __name__ == "__main__":
    asyncio.run(main())

Output:

Producing: msg-0
Consumed: msg-0
Producing: msg-1
Consumed: msg-1
Producing: msg-2
Consumed: msg-2

Explanation:

• chan() creates an unbuffered channel

• ch << msg asynchronously sends a value

• async for msg in ch: receives until the channel is closed

• go(...) spawns the producer in the background

This small example shows how channels coordinate producer-consumer patterns naturally and efficiently.

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Next Chapter

We'll now explore different types of channels (full-duplex, send-only, receive-only), and how to use split() to control access.