Can not modify global variable in an asynchronous function (coroutine) in python

Question

I run this code in jupyter notebook(python 3.6.8). I expect the code to print 2 as the result, somehow it still prints 1. I want to know why.

import asyncio
x = 1

async def func():
    global x
    x = 2
    print(x)

await func()
print(x)

And the result is:

The jupyter notebook environment I am using is:

• jupyter core : 4.6.3
• jupyter-notebook : 6.1.4
• qtconsole : 4.7.7
• ipython : 7.16.1
• ipykernel : 5.3.4
• jupyter client : 6.1.7
• jupyter lab : 2.2.9
• nbconvert : 6.0.7
• ipywidgets : 7.5.1
• nbformat : 5.1.2
• traitlets : 4.3.3

Answer 1

If you want to change a global variable in IPython coroutine you have to acquire the asyncio.Lock.

import asyncio

x = 1

async def func():
    global x
    lock = asyncio.Lock()
    await lock.acquire()
    x = 2
    lock.release()

await func()
print(x)  # 2