How can I handle exceptions in ThreadPoolExecutor?

How can I handle exceptions in ThreadPoolExecutor?

You can handle exceptions in ThreadPoolExecutor by using a try-except block within the callable function.

What if I want to collect all exceptions from multiple threads?

You can use a shared list to store exceptions and then check that list after all threads have completed.

Can you show me a code example?

Sure! Here's a simple example:

from concurrent.futures import ThreadPoolExecutor, as_completed

def task(n):
    if n == 2:
        raise ValueError('An error occurred!')
    return n * 2

exceptions = []
results = []

with ThreadPoolExecutor(max_workers=3) as executor:
    futures = {executor.submit(task, i): i for i in range(5)}
    for future in as_completed(futures):
        try:
            result = future.result()
            results.append(result)
        except Exception as e:
            exceptions.append(e)

print('Results:', results)
print('Exceptions:', exceptions)

What should I do if I want to retry failed tasks?

You can implement a retry mechanism by wrapping the task submission in a loop that attempts to resubmit the task a certain number of times.