The hash() function returns a unique integer (hash value) for an object. It’s useful for storing objects in hash-based collections like sets and dictionaries, ensuring data integrity, and optimizing lookups.
Example
num = 42
print(hash(num))
# Output: (Unique hash value)Each immutable object gets a unique, fixed hash value.
Syntax
hash(object)- object → The object to hash (must be immutable:
int,float,str,tuple). - Returns → A unique integer (hash value).
1. Hashing Strings for Fast Lookups
name = "Alice"
print(hash(name))
# Output: (Unique hash value)Hashes make string comparisons faster in dictionaries.
2. Using hash() in Sets and Dictionaries
Hashes allow fast indexing in sets and dictionary keys.
users = {"Alice", "Bob", "Charlie"}
print(hash("Alice") in map(hash, users))
# Output: TrueThis makes lookups faster than checking each item manually.
3. Hashing Tuples for Consistency
Immutable tuples can be hashed, unlike lists.
coords = (10, 20)
print(hash(coords))
# Output: (Unique hash value)Useful when storing coordinates, database records, or cache keys.
4. Objects That Cannot Be Hashed
Mutable objects like lists and dictionaries cannot be hashed.
hash([1, 2, 3])
# TypeError: unhashable type: 'list'Only immutable objects can be used as dictionary keys or set elements.
Key Notes
- ✔ Converts immutable objects into unique numbers for fast lookups.
- ✔ Used in sets and dictionary keys for quick comparisons.
- ✔ Tuples can be hashed, but lists cannot.
- ✔ Hash values may change across Python sessions (except for integers and strings).
By using hash(), you can store and retrieve data efficiently, making it essential for fast data processing and unique object identification. 🚀