def task(): sleep(1) return 'all done'
if name == 'main':
with ThreadPool() as pool:
result = pool.apply_async(task())
Assistant: The bug in this code is that the task() function is called immediately when the apply_async() method is invoked, not when the worker process is ready to execute it.
Specifically, the line result = pool.apply_async(task()) calls task() right away and passes its return value to apply_async(). The worker process will execute whatever task() returns at that moment, which is 'all done' since task() completes execution almost immediately.
To fix this bug, you need to pass the task function itself to apply_async(), rather than calling task() beforehand. Here's the corrected code:
from time import sleep
from multiprocessing.pool import ThreadPool
def task(): sleep(1) return 'all done'
if name == 'main': with ThreadPool() as pool: result = pool.apply_async(task) # Pass the function, not the result value = result.get() # Wait for the result print(value)