What is the difference between a dictionary and a set data structure?

Dictionary (dict) and set (set) are different data structures in Python, although both are based on hash tables and provide fast access.

Main differences:

• Dictionary (dict) stores pairs of "key: value". Keys are unique, and values can be any objects.
• Set (set) stores only unique elements without values.

Example:

# Dictionary
my_dict = {'apple': 3, 'banana': 5}
print(my_dict['apple'])  # 3

# Set
my_set = {'apple', 'banana', 'cherry'}
print('banana' in my_set)  # True

Thus, a dictionary is used when you need to store key-value pairs, and a set is used when the collection of unique elements without additional information is important.