aio-libs/aiohttp · critical · RuntimeError

aiohttp 4.x requires Python 3.10+

Error message

aiohttp 4.x requires Python 3.10+

What it means

Raised by setup.py at install time when the running interpreter is older than Python 3.10. aiohttp 4.x dropped support for Python < 3.10, so the build gates on sys.version_info and aborts before any extension compilation or packaging. This is a hard version floor, not a soft warning.

Source

Thrown at setup.py:9

import os
import pathlib
import sys

from setuptools import Extension, setup
from setuptools.command.build_ext import build_ext

if sys.version_info < (3, 10):
    raise RuntimeError("aiohttp 4.x requires Python 3.10+")


USE_SYSTEM_DEPS = bool(
    os.environ.get("AIOHTTP_USE_SYSTEM_DEPS", os.environ.get("USE_SYSTEM_DEPS"))
)
NO_EXTENSIONS: bool = bool(os.environ.get("AIOHTTP_NO_EXTENSIONS"))
CYTHON_TRACING: bool = bool(os.environ.get("AIOHTTP_CYTHON_TRACE"))
HERE = pathlib.Path(__file__).parent
IS_GIT_REPO = (HERE / ".git").exists()


if sys.implementation.name != "cpython":
    NO_EXTENSIONS = True


if (
    not USE_SYSTEM_DEPS
    and IS_GIT_REPO

View on GitHub (pinned to c0ef574e29)

Solutions

1. Upgrade the interpreter to Python 3.10 or newer and reinstall aiohttp in a fresh venv.
2. Pin aiohttp to the 3.x line (`aiohttp<4`) if you must stay on Python 3.9.
3. Update CI/Docker base images to a 3.10+ Python before installing.

Example fix

# before: python 3.9
pip install aiohttp  # -> RuntimeError: aiohttp 4.x requires Python 3.10+

# after: use python 3.10+
python3.10 -m venv .venv && . .venv/bin/activate
pip install aiohttp

import sys

def assert_python_310():
    if sys.version_info < (3, 10):
        raise RuntimeError("aiohttp 4.x requires Python 3.10+")

import sys

def supports_aiohttp4() -> bool:
    return sys.version_info >= (3, 10)

When it happens

Trigger: Running `pip install aiohttp` (from sdist) or `pip install -e .` in this repo on Python 3.9 or earlier. The check at setup.py:8-9 raises RuntimeError immediately.

Common situations: A project or CI image still pinned to Python 3.9 attempting to install aiohttp 4.x; upgrading aiohttp without upgrading the runtime; a base image whose default python is 3.9; an old virtualenv used to build aiohttp.

Related errors

• OPTIONS route was set already
• SSL is not supported.
• Use Python 3.11+ to run 'make sync-direct-runtime-deps'

AI-assisted analysis of aio-libs/aiohttp@c0ef574e29 (2026-08-04). Data as JSON: /data/errors/44aa01424d2cf8aa.json. Report an issue: GitHub.