tornado

library6.5.8pypypi✓ verified 30d ago

Tornado is a Python web framework and asynchronous networking library, originally developed at FriendFeed. It enables scalable, non-blocking network I/O, making it ideal for applications requiring long-lived connections, such as long polling and WebSockets. The current version is 6.5.5, with a release cadence of approximately every few months.

web-framework http-networking

pip install tornado

github ↗package ↗homepage ↗

INSTALL

IMPORT

SIG · TORNADO

tornado

web-frameworkpythonv6.5.8

Install

1.9s avg

Import

384ms

Disk

20MB

Pass rate

10/ 10

Env Coverage10 / 10

glibc

3.9–3.13

musl

3.9–3.13

Install & Compatibility

Where this runs

tested against v6.5.8 · pip install

no network on importno background threads

Install × environment matrix

Each cell = how many times install + import succeeded across repeated harness runs. Partial = flaky.
glibc = Debian/Ubuntu slim · musl = Alpine Linux

musl

py 3.10–3.95 runs

installs and imports cleanly · install 0.0s · import 0.408s · 21.2MB

glibc

py 3.10–3.95 runs

installs and imports cleanly · install 1.9s · import 0.360s · 22MB

20MB installed

● package 20MB

Code

Verified usage

Verified import paths — ran on the pinned version, not inferred.

RequestHandler

✓ from tornado.web import RequestHandler

Ensure correct import path to avoid ImportError

Application

✓ from tornado.web import Application

Ensure correct import path to avoid ImportError

IOLoop

✓ from tornado.ioloop import IOLoop

Ensure correct import path to avoid ImportError

A simple Tornado application that responds with 'Hello, world' to GET requests on the root URL.

import asyncio from tornado.web import Application, RequestHandler from tornado.ioloop import IOLoop class MainHandler(RequestHandler): def get(self): self.write('Hello, world') def make_app(): return Application([ (r'/', MainHandler), ]) async def main(): app = make_app() app.listen(8888) await asyncio.Event().wait() if __name__ == '__main__': asyncio.run(main())

Debug

Known issues

breakingIOLoop.add_callback_from_signal is deprecated and will be removed in Tornado 7.0. Use asyncio.loop.add_signal_handler instead.

fix

Replace IOLoop.add_callback_from_signal with asyncio.loop.add_signal_handler.

affects: <=6.4.0

deprecatedThe client_secret argument to OAuth2Mixin.authorize_redirect is deprecated and will be removed in Tornado 7.0.

fix

Remove the client_secret argument from OAuth2Mixin.authorize_redirect calls.

affects: <=6.4.0

gotchaTornado is not thread-safe. Ensure that Tornado objects are not accessed from multiple threads simultaneously.

fix

Use IOLoop.add_callback to schedule callbacks on the main thread.

affects: all

Errors

Common errors & fixes

No handlers could be found for logger "tornado.access"

Tornado's default access logger tries to log HTTP requests but no logging handlers are configured in the Python standard logging library for the 'tornado.access' logger.

fix

Configure Python's logging system to add a handler, for example: `import logging; logging.basicConfig(level=logging.INFO)` or configure specific handlers for `logging.getLogger('tornado.access')`.

TypeError: 'generator' object is not awaitable

This error typically occurs in Python 3.5+ when an `async def` function uses the `yield` keyword instead of `await`, or when an object that is a generator (e.g., from `@tornado.gen.coroutine` without proper conversion) is passed to `await`.

fix

Replace `yield` with `await` in `async def` functions, and ensure all asynchronous operations return awaitable objects (e.g., futures, coroutines). If using old `@tornado.gen.coroutine` code, consider converting it to `async def` or ensure it's called using `yield from` in compatible contexts.

RuntimeError: Cannot run `IOLoop.run_sync` without a current IOLoop

`IOLoop.run_sync()` is called from a context (e.g., a new thread or script without a Tornado application running) where no `IOLoop` has been initialized or set as the current IOLoop for that thread.

fix

Ensure `IOLoop.current()` is available and initialized in the execution context where `run_sync` is called. If running async code from a synchronous entry point, start the IOLoop first, e.g., `IOLoop.current().start()` or `IOLoop.current().run_sync(your_async_function)` within an already running IOLoop's context.

AttributeError: module 'tornado' has no attribute 'web'

This happens when the `tornado` package is imported generally (e.g., `import tornado`), but submodules like `web` are then accessed as direct attributes of the `tornado` module, which is incorrect.

fix

Import the specific submodule directly: `from tornado import web` or `import tornado.web`.

Upgrade

Version history

6.5.8latest on PyPI · released Aug 7, 2026

Audit

Dependencies

asynciorequiredTornado integrates with asyncio for asynchronous programming

Agent activity

22 hits · last 30 days

node

OpenAI (training)

Resources

githubhttps://github.com/tornadoweb/tornado ↗

packagehttps://pypi.org/project/tornado/ ↗

homepagehttp://www.tornadoweb.org/ ↗