Specialized containers
The collections module provides containers designed around common programming patterns. Counter counts values, defaultdict simplifies grouping, and deque is optimized for adding and removing items at both ends.
Choose the container for the operation
A normal dictionary is excellent for ordinary mappings, but a defaultdict(list) can make grouping code much clearer. A queue implemented with repeated pop(0) on a list can be replaced by a deque.
Readable data processing
Specialized containers are valuable because they communicate intent. A reader can immediately understand that a Counter represents frequency information or a deque represents queue-like data.
Practice: group orders by customer ID, count each customer's orders and use a deque to model a small processing queue.
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