Non Blocking Channel Operations in Python

Basic sends and receives on channels are blocking in Python's `asyncio` library. However, we can use `asyncio.wait()` with a timeout to implement non-blocking operations, similar to the `select` with a `default` clause in other languages.

```python
import asyncio

async def main():
    messages = asyncio.Queue()
    signals = asyncio.Queue()

    # Here's a non-blocking receive. If a value is
    # available on `messages` then it will be retrieved.
    # If not, it will immediately move on.
    try:
        msg = await asyncio.wait_for(messages.get(), timeout=0.01)
        print(f"received message {msg}")
    except asyncio.TimeoutError:
        print("no message received")

    # A non-blocking send works similarly. Here `msg`
    # is attempted to be sent to the `messages` queue,
    # but if it can't be sent immediately, it moves on.
    msg = "hi"
    try:
        await asyncio.wait_for(messages.put(msg), timeout=0.01)
        print(f"sent message {msg}")
    except asyncio.TimeoutError:
        print("no message sent")

    # We can use multiple try-except blocks to implement
    # a multi-way non-blocking select. Here we attempt
    # non-blocking receives on both `messages` and `signals`.
    done, pending = await asyncio.wait([
        messages.get(),
        signals.get()
    ], timeout=0.01, return_when=asyncio.FIRST_COMPLETED)

    if done:
        for task in done:
            result = task.result()
            if task == messages.get():
                print(f"received message {result}")
            elif task == signals.get():
                print(f"received signal {result}")
    else:
        print("no activity")

asyncio.run(main())

To run the program:

$ python non_blocking_queue_operations.py
no message received
no message sent
no activity

This Python code demonstrates non-blocking operations using asyncio.Queue and asyncio.wait(). While Python doesn’t have built-in channels like some other languages, the asyncio.Queue provides similar functionality in asynchronous contexts. The asyncio.wait_for() function is used to implement timeouts, effectively creating non-blocking operations.

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Non Blocking Channel Operations in Python