如何重用 aiohttp.ClientSession？

Question

I am building own async python package and faced the problem.

This is my code:

class Client:
    """
    Async client for making requests
    """

    def __init__(self, base_url: str = BASE_URL) -> None:
        self.base_url = base_url
        self.session = ClientSession()

    async def get(self, method: str, *args: tp.Any, **kwargs: tp.Any) -> tp.Any:
        async with self.session.get(f'{self.base_url}/{method}', *args, **kwargs) as response:
            data = await response.json()
            return data

When I try to use something like this:

await client.get()

I get

RuntimeError: Timeout context manager should be used inside a task

I suppose that the reason of this error is calling ClientSession() not inside the coroutine. But I hope that somebody knows the way to re-use ClientSession()

I have already read other similar questions, but they are not suitable to my situation.

Answer 1

You can initialize (and cache) the session when needed:

class Client:
    """
    Async client for making requests
    """

    def __init__(self, base_url: str = BASE_URL) -> None:
        self.base_url = base_url
        self.session = None

    async def get(self, method: str, *args: tp.Any, **kwargs: tp.Any) -> tp.Any:
        if not self.session:
            self.session = ClientSession()
        async with self.session.get(f'{self.base_url}/{method}', *args, **kwargs) as response:
            data = await response.json()
            return data

Depending on how you use the Client you can also use a class attribute for the session object.