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aiter() 函数

aiter() 函数从异步可迭代对象中返回一个异步迭代器。

复杂度参考

操作 时间 空间 备注
aiter() O(1) O(1) 另加一次 __aiter__() 调用，并返回其结果；参数没有 __aiter__() 或结果没有 __anext__() 时引发 TypeError
异步生成器的 __aiter__() O(1) O(1) 返回生成器自身

基本用法

创建异步迭代器

import asyncio

async def async_generator():
    for i in range(3):
        yield i

async def main():
    # Get the async iterator - O(1): an async generator is its own
    async_iter = aiter(async_generator())

    # Iterate
    value = await async_iter.__anext__()
    print(value)  # 0

asyncio.run(main())

从异步可迭代对象获取

import asyncio

class AsyncIterable:
    def __aiter__(self):
        return AsyncIterator()

class AsyncIterator:
    def __init__(self):
        self.count = 0

    def __aiter__(self):
        return self

    async def __anext__(self):
        if self.count >= 3:
            raise StopAsyncIteration
        self.count += 1
        return self.count

async def main():
    # Get iterator from iterable - O(1)
    iterator = aiter(AsyncIterable())

    # Use with async for
    async for value in iterator:
        print(value)  # 1, 2, 3

asyncio.run(main())

配合 async for 使用

import asyncio

async def fetch_data(urls):
    """Simulate async data fetching."""
    for url in urls:
        await asyncio.sleep(0.1)
        yield f"Data from {url}"

async def main():
    urls = ["url1", "url2", "url3"]

    # aiter is implicit in async for
    async for data in fetch_data(urls):
        print(data)

asyncio.run(main())

与 iter() 的比较

import asyncio

# iter() - synchronous iterator - O(1)
def sync_generator():
    yield 1
    yield 2

sync_iter = iter(sync_generator())
print(next(sync_iter))  # Works synchronously

# aiter() - asynchronous iterator - O(1)
async def async_generator():
    yield 1
    yield 2

async def main():
    async_iter = aiter(async_generator())
    print(await async_iter.__anext__())  # Must be awaited

asyncio.run(main())

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