What are some examples of async iterators in Python?

What are some examples of async iterators in Python?

Async iterators in Python allow you to iterate over data asynchronously. Here's a simple example:

import asyncio

class AsyncIterator:
    def __init__(self, n):
        self.n = n
        self.current = 0

    def __aiter__(self):
        return self

    async def __anext__(self):
        if self.current < self.n:
            await asyncio.sleep(1)  # Simulate an async operation
            self.current += 1
            return self.current
        else:
            raise StopAsyncIteration

async def main():
    async for number in AsyncIterator(5):
        print(number)

asyncio.run(main())

Can you explain how this example works?

Sure! In this example, AsyncIterator is a custom async iterator class. The __aiter__ method returns the iterator object itself, and the __anext__ method is called to get the next value. It uses await asyncio.sleep(1) to simulate an asynchronous operation, yielding a number from 1 to 5 with a 1-second delay between each.

What are some real-world use cases for async iterators?

Async iterators are useful in scenarios like streaming data from APIs, reading large files asynchronously, or processing data from databases without blocking the main thread. They help improve performance in I/O-bound applications.

Can you provide another example of an async iterator?

Certainly! Here's another example that fetches data from a list of URLs asynchronously:

import aiohttp
import asyncio

class AsyncURLFetcher:
    def __init__(self, urls):
        self.urls = urls

    def __aiter__(self):
        self.session = aiohttp.ClientSession()
        return self

    async def __anext__(self):
        if not self.urls:
            await self.session.close()
            raise StopAsyncIteration
        url = self.urls.pop(0)
        async with self.session.get(url) as response:
            return await response.text()

async def main():
    urls = ['http://example.com', 'http://example.org']
    async for content in AsyncURLFetcher(urls):
        print(content)

asyncio.run(main())