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2.2 Dictionaries & Sets: Hash Tables & O(1) Lookups
Topic Summary
Learn how Python dictionaries achieve O(1) lookups using compact hash tables and why dictionary keys must be hashable.
What You Will Learn
• Explain hash table mechanics behind `dict` and `set`.
• Understand hashability: why lists cannot be dictionary keys.
• Use `.get(key, default)` and `setdefault()` defensively.
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