In the Python docs about Context Vars a Context::run method is described to enable executing a callable inside a context so changes that the callable perform to the context are contained inside the copied Context. Though what if you need to execute a coroutine? What are you supposed to do in order to achieve the same behavior?

In my case, what I wanted was something like this to handle a transactional context with possible nested transactions:

my_ctxvar = ContextVar("my_ctxvar")async def coro(func, transaction):token = my_ctxvar.set(transaction)r = await func()my_ctxvar.reset(token)  # no real need for this, but why not eitherreturn rasync def foo():ctx = copy_context()# simplification to one case here: let's use the current transaction if there is oneif tx_owner := my_ctxvar not in ctx:tx = await create_transaction()else:tx = my_ctxvar.get()try:r = await ctx.run(coro)  # not actually possibleif tx_owner:await tx.commit()except Exception as e:if tx_owner:await tx.rollback()raise from ereturn r

As I already pointed out here, context variables are natively supported by asyncio and are ready to be used without any extra configuration. It should be noted that:

• Сoroutines executed by the current task by means of await share the same context
• New spawned tasks by create_task are executed in the copy of parent task context.

Therefore, in order to execute a coroutine in a copy of the current context, you can execute it as a task:

await asyncio.create_task(coro())

Small example:

import asyncio
from contextvars import ContextVarvar = ContextVar('var')async def foo():await asyncio.sleep(1)print(f"var inside foo {var.get()}")var.set("ham")  # change copyasync def main():var.set('spam')await asyncio.create_task(foo())print(f"var after foo {var.get()}")asyncio.run(main())

var inside foo spam
var after foo spam