sortedcontainers

Using sortedcontainers feels remarkably natural - the API mirrors Python's built-in list, dict, and set interfaces almost perfectly. You can switch from a regular list to a SortedList with minimal code changes, and operations like bisect_left, bisect_right are built right in. The pure-Python implementation means no compilation headaches, and it's consistently faster than alternatives like blist in real-world scenarios.

The documentation is thorough with clear performance characteristics documented for every operation. Type hints are present but basic - you get SortedList[int] support, but the experience isn't as polished as modern typed libraries. Error messages are straightforward Python exceptions without special handling. One gotcha: mutable keys in SortedDict can break sorting invariants silently, which you only discover through careful reading.

Day-to-day usage is friction-free. IDE autocomplete works well since it follows standard collection protocols. The library is stable (no breaking changes in years) but also hasn't seen updates recently, which can be viewed either as rock-solid maturity or minimal maintenance depending on your perspective.

This library has been a reliable workhorse in production systems for years. The API is clean and intuitive - SortedList, SortedDict, and SortedSet behave exactly like their standard library counterparts with added ordering guarantees. Performance is surprisingly good for pure Python; the load factor tuning means you're not constantly resorting on inserts. Memory footprint is predictable and reasonable, making capacity planning straightforward.

What I appreciate most is the zero-dependency footprint and stability. No compilation requirements, no native extensions breaking across Python versions, and the 2.x series has been rock solid with no breaking changes in years. Error handling is straightforward - you get sensible TypeErrors for non-comparable items, and behavior is deterministic under all conditions I've tested. The library includes no logging hooks or observability features, but that's actually a plus - it's a pure data structure with no side effects or hidden behaviors.

The documentation includes complexity guarantees for every operation, which is invaluable for performance planning. Thread safety story is clear: not thread-safe by default, wrap with locks as needed. No connection pooling concerns, no retries, no timeouts - it's just a data structure doing exactly what it should.

The learning curve is virtually non-existent if you know Python's built-in containers. The API mirrors list, dict, and set semantics so closely that you can drop SortedList, SortedDict, or SortedSet into existing code with minimal changes. The documentation is exceptional—comprehensive API reference paired with a performance comparison guide and a detailed tutorial that covers real-world scenarios like maintaining sorted rankings or implementing priority queues.

Error messages are standard Python exceptions, which means debugging is straightforward. When you pass non-comparable objects, you get clear TypeErrors just like with sorted(). The package handles edge cases gracefully, and I've never encountered surprising behavior. GitHub issues get responses within days, and there's a healthy Stack Overflow presence with good coverage of common patterns.

What really stands out is how the common use cases just work. Need to maintain a sorted list while inserting elements? `sl.add(item)` handles it. Want to find elements by index or bisect by value? Both operations are optimized and intuitive. The library gets out of your way and lets you focus on your problem, not on managing sorted data structures.