Queue.Queue vs. collections.deque

I need a queue which multiple threads can put stuff into, and multiple threads may read from.

Python has at least two queue classes, Queue.Queue and collections.deque, with the former seemingly using the latter internally. Both claim to be thread-safe in the documentation.

However, the Queue docs also state:

collections.deque is an alternative
implementation of unbounded queues
with fast atomic append() and
popleft() operations that do not
require locking.

Which I guess I don’t quite unterstand: Does this mean deque isn’t fully thread-safe after all?

If it is, I may not fully understand the difference between the two classes. I can see that Queue adds blocking functionality. On the other hand, it loses some deque features like support for the in-operator.

Accessing the internal deque object directly, is

x in Queue().deque

thread-safe?

Also, why does Queue employ a mutex for it’s operations when deque is thread-safe already?

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