Queuelib is a Python library providing persistent and in-memory queue data structures. It implements FIFO, LIFO, priority, and round-robin queues with disk-based storage options for durability. The library is dependency-free, using only the Python standard library, and is designed for scenarios requiring reliable queuing such as web crawlers. Architecture consists of modular components: base queue classes in queue.py, priority queue in pqueue.py, and round-robin queue in rrqueue.py. Disk-based queues manage data through chunk files (FIFO) or single files (LIFO) with careful bookkeeping to survive process restarts. The priority and round-robin queues use a factory pattern to decouple queue logic from storage implementation, enabling flexibility.