Why is Python's OrderedDict ordered?
6 months ago
- #Python
- #OrderedDict
- #Data Structures
- Python dictionaries preserve insertion order since Python 3.7.
- collections.OrderedDict was used before built-in dictionaries preserved order.
- OrderedDict remains in the standard library for backward compatibility, different equality behavior, and extra features like move_to_end().
- OrderedDict uses a doubly linked list and another dictionary to maintain order efficiently.
- The implementation ensures dictionary operations remain O(1) time complexity.
- Weak references are used to avoid reference cycles in the linked list.
- A sentinel object() is used as a default value in pop() to distinguish between existing and missing keys.