asyncio

Library to write concurrent code using the async/await syntax. asyncio is often a perfect fit for IO-bound and high-level structured network code. Python documentation

Асинхронный python без головной боли ¹

Series of articles.

What is a coroutine in general, how it’s modify function behavior?
A coroutine gives the interpreter the ability to resume a base function that was suspended at the location where the await keyword was placed.

If function contains await keyword it can be called as a coroutine.
Strictly speaking no, it’s what function with await returning (coroutine object). async def f is asynchronous function, f() is coroutine object.

Synchronous code:

import time
 
def fun1(x:int):
    print(f"Function 1 result {x**2}, wait ...")
    time.sleep(3)
    print("Function 1 finished")
 
def fun2(x:float):
    print(f"Function 2 result {x**.05}, wait ...")
    time.sleep(3)
    print("Function 2 finished")
 
def main():
    fun1(4)
    fun2(4)
 
print(time.strftime("%X"))
main()
print(time.strftime("%X"))

Asynchronous code example, imagine that there is no async/await, then this code will be easier to read:

import asyncio
import time
 
# async prefix, function must run asynchronically
async def fun1(x: int):
    print(f"Function 1: result {x**2}, wait ...")
 
    # await (like hey you can execute another function, I'll sleep 3 seconds)
    # asynchronical sleep (coroutine) which doesnt' block intrpereter
    await asyncio.sleep(3)
 
    print("Function 1: finished")
 
 
async def fun2(x: float):
    print(f"Function 2: result {x**.05}, wait ...")
 
    await asyncio.sleep(3)
 
    print("Function 2: finished")
 
 
async def main():
    fun1_corutine_task_wrapper = asyncio.create_task(
        fun1(4, break_async)
    )  # schedule execution of coroutine task (fun1)
 
    fun2_corutine_task_wrapper = asyncio.create_task(fun2(4))
 
    await fun1_corutine_task_wrapper  # switching point #1 to the task wrapper
    await fun2_corutine_task_wrapper  # switching point #2 to the task wrapper
 
 
print(time.strftime("%X"))
 
# Execute main coroutine, need to pass an async function with await to Task's!
asyncio.run(main())
 
print(time.strftime("%X"))

Asynchronous context managers:

python - How does asyncio actually work? - Stack Overflow

References

Footnotes

1. Асинхронный python без головной боли (часть 1) / Хабр ↩