Why can't i append to manager.list()?

Question

The output should be: [[], ['new element'], []] but is [[], [], []] just blank. Why?

from multiprocessing import Manager

if __name__ == '__main__':# Create a Manager object
    manager = Manager()

    # Create a shared list of lists
    shared_list = manager.list([[], [], []])

    # Append an element to the second index
    element = "New Element"
    shared_list[1].append(element)

    # Print the updated shared list
    print(shared_list)

Answer 1

Because you aren't appending to the manager.list anywhere. You are retrieving a value, which copies a new object into your current process. That value is a list, when you then append to. But the manager.list has no way of knowing that. From the docs:

If standard (non-proxy) list or dict objects are contained in a referent, modifications to those mutable values will not be propagated through the manager because the proxy has no way of knowing when the values contained within are modified. However, storing a value in a container proxy (which triggers a __setitem__ on the proxy object) does propagate through the manager and so to effectively modify such an item, one could re-assign the modified value to the container proxy

So you could do:

inner = shared_list[1]
inner.append(element)
shared_list[1] = inner