# What’s new in aiohttp 3.0

## async/await everywhere

The main change is dropping `yield from` support and using `async`/`await` everywhere. Farewell, Python 3.4.

The minimal supported Python version is 3.5.3 now.

Why not 3.5.0? Because 3.5.3 has a crucial change: `asyncio.get_event_loop()` returns the running loop instead of default, which may be different, e.g.:

    loop = asyncio.new_event_loop()
    loop.run_until_complete(f())

Note, `asyncio.set_event_loop()` was not called and default loop is not equal to actually executed one.

## Application Runners

People constantly asked about ability to run aiohttp servers together with other asyncio code, but `aiohttp.web.run_app()` is blocking synchronous call.

aiohttp had support for starting the application without `run_app` but the API was very low-level and cumbersome.

Now application runners solve the task in a few lines of code, see Application runners for details.

## Client Tracing

Other long awaited feature is tracing client request life cycle to figure out when and why client request spends a time waiting for connection establishment, getting server response headers etc.

Now it is possible by registering special signal handlers on every request processing stage. Client Tracing provides more info about the feature.

## HTTPS support

Unfortunately asyncio has a bug with checking SSL certificates for non-ASCII site DNS names, e.g. https://историк.рф or https://雜草工作室.香港.

The bug has been fixed in upcoming Python 3.7 only (the change requires breaking backward compatibility in `ssl` API).

aiohttp installs a fix for older Python versions (3.5 and 3.6).

## Dropped obsolete API

A switch to new major version is a great chance for dropping already deprecated features.

The release dropped a lot, see Changelog for details.

All removals was already marked as deprecated or related to very low level implementation details.

If user code did not raise `DeprecationWarning` it is compatible with aiohttp 3.0 most likely.

## Summary

Enjoy aiohttp 3.0 release!

The full change log is here: Changelog.