CODEWITHSUNDEEP
pythonpython-3.xmultithreadingexceptionpython-multithreading
WoJ
WoJ

Reputation: 29987

How to catch exceptions from multiple threads?

I have a set of functions I would like to execute in threads. Some of these functions may raise a specific exception I would like to catch, separately for each thread.

I tried something along the lines of

import threading

class MyException(Exception):
    pass

def fun():
    raise MyException

myfuns = [threading.Thread(target=fun), threading.Thread(target=fun)]
for myfun in myfuns:
    try:
        myfun.start()
    except MyException:
        print("caught MyException")

I expected to see caught MyException twice, one for each thread. But there is only one.

Is it possible to catch exceptions in threads independently of each other? (in other words: when a thread raises an exception, manage it in the code that called the thread?)

Upvotes: 4

Views: 1598

Answers (1)

wwii
wwii

Reputation: 23753

For Python 3.8+ you can define a handler for uncaught exceptions.

import threading

def f(args):
    print(f'caught {args.exc_type} with value {args.exc_value} in thread {args.thread}\n')
    
threading.excepthook = f

class MyException(Exception):
    pass

def fun():
    raise MyException

myfuns = [threading.Thread(target=fun), threading.Thread(target=fun)]
for myfun in myfuns:
    myfun.start()
for myfun in myfuns:
    myfun.join()

Upvotes: 6

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