Explain what a hash function is and what it is used for.

A hash function is an algorithm that transforms input data (such as a string or file) into a fixed-size string or number, called a hash or hash code. The main properties of a hash function:

• Fast computation of the hash for any data.
• The same input always produces the same hash.
• Different data likely produce different hashes (collision minimization).

In programming, hash functions are used for:

• Fast data lookup and comparison (e.g., in hash tables or dictionaries).
• Data integrity verification.
• Cryptographic purposes (hashing passwords, digital signatures).

Example in Python:

# Getting the hash of a string
s = "example"
h = hash(s)
print(h)

Here, the hash function returns an integer hash of the object.