Question

I am in this scenario: at a certain point, the main thread need to wait until another thread is started(alive). How can I notify the main thread?

I do not want to write a loop and keep the main thread busy waiting. Thanks a lot.

Answer 1

Use threading.Semaphore where your main thread will call acquire after calling start on the second thread. When the second thread is started to the point you want it will call release on the same semaphore.

If the second thread calls release first then the main thread will return from the acquire immediately. If the main thread calls acquire first then it will block until the second thread calls release.

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Use threading.Condition where a single condition variable is made available to the main thread and the second thread. The main thread can then wait on the variable after it has started the second thread. When the second thread is up it can change the variable and then issue a notify on it.