A dictionary is a data structure in programming that stores a collection of key-value pairs. Each key in the dictionary is and associated with a specific value. It is similar to a physical dictionary where words (keys) have corresponding (values). In dictionaries, keys are used to access their corresponding values, allowing for efficient data retrieval as the unique keys provide a direct mapping to the desired values. Creating a dictionary in Python is done using curly braces ({}) and key-value pairs by a colon (:).
To access the values in a dictionary, we can use the corresponding . For example, if we have a dictionary called `student`, we can access the name with `student["name"]`, which outputs: . Dictionaries also allow us to modify the values associated with existing keys. By simply assigning a new value to a key, we can change the information it holds. For instance, if we wanted to change the grade of a student, we would use `student["grade"] = "12th"` to update the value.
Dictionaries can be quite versatile. For example, we can create a contact list in Python where each person's information, such as telephone numbers and emails, can be stored. In this case, the keys would be the name, and the values could be another dictionary containing their telephone number and email address. We can access this information by referencing the name as the key and the respective attribute as a sub-key.
Furthermore, Python dictionaries are implemented using a technique known as hash . This method provides fast data retrieval by mapping keys to values using a hash function, ensuring efficient storage and quick access. The key advantage of using a hash table is the average O(1) time complexity for lookups, insertions, and deletions, making it very fast to access or modify elements, regardless of the of the dictionary.
