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Python 3.6 addedasync generators. (What's an asyncgenerator?Check out my 5-minute lightning talk demo from PyCon 2016.) Python 3.7 adds some moretools to make them usable, likecontextlib.asynccontextmanager.

This library gives you all that back to Python 3.5.

For example, this code only works in Python 3.6+:

asyncdefload_json_lines(stream_reader):asyncforlineinstream_reader:yieldjson.loads(line)

But this code does the same thing, and works on Python 3.5+:

fromasync_generatorimportasync_generator,yield_@async_generatorasyncdefload_json_lines(stream_reader):asyncforlineinstream_reader:awaityield_(json.loads(line))

Or in Python 3.7, you can write:

fromcontextlibimportasynccontextmanager@asynccontextmanagerasyncdefbackground_server():asyncwithtrio.open_nursery()asnursery:value=awaitnursery.start(my_server)try:yieldvaluefinally:# Kill the server when the scope exitsnursery.cancel_scope.cancel()

This is the same, but back to 3.5:

fromasync_generatorimportasync_generator,yield_,asynccontextmanager@asynccontextmanager@async_generatorasyncdefbackground_server():asyncwithtrio.open_nursery()asnursery:value=awaitnursery.start(my_server)try:awaityield_(value)finally:# Kill the server when the scope exitsnursery.cancel_scope.cancel()

(And if you're on 3.6, you can use@asynccontextmanager withnative generators.)

• Install:python3 -m pip install -U async_generator (or on Windows,maybepy -3 -m pip install -U async_generator
• Manual:https://async-generator.readthedocs.io/
• Bug tracker and source code:https://github.com/python-trio/async_generator
• Real-time chat:https://gitter.im/python-trio/general
• License: MIT or Apache 2, your choice
• Contributor guide:https://trio.readthedocs.io/en/latest/contributing.html
• Code of conduct: Contributors are requested to follow ourcode ofconduct inall project spaces.

Trio is a new async concurrencylibrary for Python that's obsessed with usability and correctness – wewant to make iteasy to get thingsright. Theasync_generatorlibrary is maintained by the Trio project as part of that mission, andbecause Trio usesasync_generator internally.

You can useasync_generator with any async library. It works greatwithasyncio, or Twisted, or whatever you like. (But we think Triois pretty sweet.)