Python Hash Table vs Dictionary: Key Differences

In Python, dictionaries are a data structure based on hash tables. Therefore, there is a close relationship between hash tables and dictionaries, but there are also some differences.

1. Implementation: A hash table is a versatile data structure that can be used to solve multiple problems, while a dictionary is a specific data structure based on a hash table.
2. Key types: Hash tables can use any hashable object as a key, such as numbers, strings, tuples, etc., while dictionary keys must be immutable objects, often strings or numbers.
3. Duplicate keys: Hash tables can have duplicate keys, while keys in a dictionary must be unique. If a duplicate key is encountered, the later key will override the previous key.
4. Order: The key-value pairs in a hash table are unordered, while the key-value pairs in a dictionary are ordered. Starting from Python 3.7, the insertion order of a dictionary will be preserved.
5. Memory usage: Hash tables may consume a significant amount of memory when storing large amounts of data, while dictionaries tend to save more memory when storing large amounts of data.

In general, a dictionary is a specific implementation of a hash table with stricter limitations and higher efficiency. In most cases, we use dictionaries instead of directly using hash tables.