Python Asynchronous Programming (asyncio)
asyncio is a library to write concurrent code using the async/await syntax. It is used as a foundation for multiple Python asynchronous frameworks that provide high-performance network and web-servers, database connection libraries, distributed task queues, etc.
Basics
Coroutines
Coroutines are declared with the async def syntax.
import asyncio
async def main():
print('Hello ...')
await asyncio.sleep(1)
print('... World!')
asyncio.run(main())Awaitables
We say that an object is an awaitable object if it can be used in an await expression. There are three main types of awaitable objects: coroutines, Tasks, and Futures.
Running Concurrent Tasks
The asyncio.gather() function allows you to run multiple coroutines concurrently.
import asyncio
import time
async def say_after(delay, what):
await asyncio.sleep(delay)
print(what)
async def main():
print(f"started at {time.strftime('%X')}")
await asyncio.gather(
say_after(1, 'hello'),
say_after(2, 'world')
)
print(f"finished at {time.strftime('%X')}")
asyncio.run(main())Creating Tasks
The asyncio.create_task() function is used to schedule the execution of a coroutine.
import asyncio
async def my_task():
print("Task started")
await asyncio.sleep(1)
print("Task finished")
async def main():
task = asyncio.create_task(my_task())
print("Main continues...")
await task
asyncio.run(main())