Asynchronous Generators and Iterators

Introduction

Async generators yield values asynchronously, useful for streaming data and processing sequences.

Async Generator

async def count_up_to(n):
    for i in range(n):
        yield i
        await asyncio.sleep(0.5)

async def main():
    async for value in count_up_to(5):
        print(value)

asyncio.run(main())

Async Comprehensions

async def fetch_values():
    for i in range(5):
        yield i * 2
        await asyncio.sleep(0.1)

async def main():
    # List comprehension
    result = [x async for x in fetch_values()]
    
    # Set comprehension
    unique = {x async for x in fetch_values()}

Async Iteration

class AsyncCounter:
    def __init__(self, n):
        self.n = n
        self.current = 0
    
    def __aiter__(self):
        return self
    
    async def __anext__(self):
        if self.current >= self.n:
            raise StopAsyncIteration
        value = self.current
        self.current += 1
        await asyncio.sleep(0.1)
        return value

async def main():
    async for i in AsyncCounter(5):
        print(i)

Practice Problems

1. Create async generator for paginated API
2. Process items with async comprehensions
3. Build async iterator for WebSocket messages
4. Combine async generators with gather
5. Implement async generator with filtering