what's the difference of calling a normal function from async function with await a coroutine from an async function?

Question

1. async def caller():
       await bar()
       print("finish")
   
   async def bar():
      // some code here
   

2. async def caller():
       bar()
       print("finish")
   
   def bar():
      //some code here
   

In above example. caller has to wait for the completion of bar() for both cases. Any difference for bar to be a normal / coroutine for this situation? If we want to "await" some functions, why not just use a normal function.

Answer 1

The difference is that in the second example bar() is a non-async function, so it itself cannot await anything. For example, if you wanted to access a web service from within bar(), it wouldn't be a problem in the first example, you'd just use aiohttp. In the second example it would be pretty much impossible, as async libraries require being used from async functions, and non-async libraries will block the whole event loop while waiting for response.

If we want to "await" some functions, why not just use a normal function.

If the function you await doesn't need to communicate with the outside world (e.g. if it just shuffles data in a dict or so), it can and should be a normal function. On the other hand, if it needs to do IO, it should be an async function.