Do I Need To Use Threading Locks In This Example?

I append values to a nested list in one thread, and I copy the growing nested list with list comprehension in the main thread. Do I need to use threading locks in my example? I kno

Solution 1:

I think you need a lock at least for iterating in one thread while appending in the other, and I think it wouldn't make sense to use a lock when copying the data when you don't use a lock when appending to the list. The point of using a lock is to claim some ownership on the list.

Another question that you may ask is what is the point of not using a lock ? You could keep your code clean by simply replacing self.data = [] by self.data = MySafeList() and by writing separately a small thread safe list class with a lock. It could be written very easily by using one of the numerous @synchronized decorators available here and there. For example the __iter__ method that allows list comprehension could be written as

@synchronized
def __iter__(self):
    return iter(list(list.__iter__(self)))