Can you explain the structure and principles of a dictionary in Python?

A dictionary in Python is a mutable data structure that stores key-value pairs. It is based on a hash table, which provides fast access to values by key.

Main principles:

• Keys must be hashable (e.g., strings, numbers, tuples with immutable elements).
• When adding a key-value pair, the key is hashed, and the hash determines the index in the array.
• If a collision occurs (two keys with the same hash), Python uses open addressing to find the next free slot.
• When searching for a value by key, the key is hashed, and the keys are checked for an exact match.

Example of using a dictionary:

my_dict = {'apple': 5, 'banana': 3}
print(my_dict['apple'])  # Outputs 5
my_dict['orange'] = 7  # Adding a new pair