Coroutine Patterns

Introduction

Coroutines are special generators that can receive values from outside. They enable producer-consumer patterns and data pipelines with bidirectional communication.

Basic Coroutine

def coroutine_example():
    while True:
        value = yield
        print(f"Received: {value}")

coro = coroutine_example()
next(coro)  # Prime the coroutine
coro.send("Hello")
coro.send("World")
coro.close()

Producer-Consumer

def producer(target):
    for i in range(10):
        target.send(i)
    target.close()

def consumer():
    while True:
        try:
            value = yield
            print(f"Consumed: {value}")
        except StopIteration:
            break

c = consumer()
next(c)
producer(c)

Pipeline with Coroutines

def source(max_val):
    for i in range(max_val):
        yield i

def filter_transform(target):
    while True:
        value = yield
        if value % 2 == 0:
            target.send(value * 2)

def sink():
    while True:
        value = yield
        print(f"Sink received: {value}")

# Connect pipeline
sk = sink()
next(sk)
ft = filter_transform(sk)
next(ft)
for i in range(5):
    ft.send(i)

Coroutine with Return Value

def aggregate():
    total = 0
    count = 0
    while True:
        value = yield
        if value is None:
            break
        total += value
        count += 1
    yield total / count if count > 0 else 0

agg = aggregate()
next(agg)
for i in [10, 20, 30]:
    agg.send(i)
avg = agg.send(None)
print(f"Average: {avg}")

Exception Handling

def error_handling_coroutine():
    try:
        while True:
            try:
                value = yield
                print(f"Processed: {value}")
            except ValueError as e:
                print(f"Caught error: {e}")
    except GeneratorExit:
        print("Coroutine closed")

coro = error_handling_coroutine()
next(coro)
coro.send(10)
coro.throw(ValueError("Test error"))
coro.close()

Practice Problems

1. Implement producer-consumer with coroutines
2. Create filter-transform pipeline
3. Handle exceptions in coroutines
4. Build coroutine with return values
5. Implement broadcast pattern