ContextVars across modules

I am completely newb on asyncio and ContextVars, I just read up what's new in 3.7 and discovered ContextVars, I struggle to understand it's usage, all I know it's helpful in coroutines, instead of using thread.local should use ContextVars. But none of the official doc and top google search result could help me truely understand its purpose.

So is convextvars shared across modules? I tried:

example.py

from contextvars import ContextVar

number = ContextVar('number', default=100)
number.set(1)

then I try to import number.py

(playground) Jamess-MacBook-Pro-2:playground jlin$ python3.7
Python 3.7.0 (v3.7.0:1bf9cc5093, Jun 26 2018, 23:26:24) 
[Clang 6.0 (clang-600.0.57)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import example
>>> from contextvars import ContextVar
>>> number = ContextVar('number', default=200)
>>> number.get()
200

I was expecting number.get() would return 1, but obviously I have understood its purpose wrong.

Could someone please help me understand this?

from ContextVars across modules