Sync code to async, without rewriting the function

Question

Basically I have synchronous code something similar to this:

def f(.):
   ...
def call(.):
   ..Some sync code..
   try:
      resp = f(..)
      ...some more transformations of resp...
          return ..
   except:
      ..Some error handling..

async def af(.):
    ...

Basically I want to dynamically alter the code of call so that it can call and await af function instead of f. Is there a way around this? I have found syncit on github, but it doesn't seem to be a solution to me as you have to rewerite the code to async first and then downgrade it to sync. Any help will be appreciated.

Answer 1

Here are two options mixing synchronous and asynchronous code.

Given

import asyncio

import trio

from unsync import unsync

Code

Option 1 - trio

Given sync code (call), call an async function via trio (async_div):

# Sync code
def call(x, y):
    """Return an awaited result."""
    try:
        resp = async_div(x, y)
    except ZeroDivisionError:
        return "Caught an exception."
    return resp
    

# Wrapper
def async_div(*args):
    """Return results from an async function."""
    return trio.run(_async_div, *args)


# Async code
async def _async_div(x, y):
    """Return an async result."""
    await trio.sleep(3)
    return x / y

Option 2 - unsync

Decorate the async code with @unsync and call the result():

# Sync code
def call(x, y):
    """Return an awaited result."""
    try:
        resp = async_div(x, y).result()
    except ZeroDivisionError:
        return "Caught an exception."
    return resp


# Async code
@unsync
async def async_div(x, y):
    """Return an async result."""
    await asyncio.sleep(3)
    return x / y

Demo

After the prescribed delay (3 secs), the results are the same:

call(0, 1)
# 0.0

call(1, 0)
# 'Caught an exception.'

See Also

Some additional resources:

• docs on trio
• Talk Python interview with trio creator N. Smith for more details and his philosophy on asynchronous programming.
• Python Bytes episode 73, item 6 on quick unsync details
• M. Kennedy's webinar demo on using unsync to speed up requests