What Is Dictionary in Advanced Data Structure?


Scott Campbell

A dictionary is an advanced data structure in computer science that stores key-value pairs. It is also known as an associative array, map, or hash table.

In a dictionary, each key is unique and associated with a value. This allows efficient retrieval of values using their corresponding keys.

Creating a Dictionary

To create a dictionary in Python, you can use curly braces ({}) or the built-in dict() function. Here’s an example:

my_dict = {'apple': 1, 'banana': 2, 'cherry': 3}

In this example, the keys are strings (‘apple’, ‘banana’, and ‘cherry’) and the values are integers (1, 2, and 3). However, dictionaries in Python can have keys of any immutable data type (such as strings, numbers, or tuples).

Accessing Values in a Dictionary

You can access the values in a dictionary by referencing their respective keys. Here’s an example:


This will output 1, which is the value associated with the key ‘apple’.

Modifying Values in a Dictionary

You can modify the value associated with a specific key in a dictionary by simply assigning a new value to it. Here’s an example:

my_dict['banana'] = 5

This will update the value associated with the key ‘banana’ to 5. The output will be:

{'apple': 1, 'banana': 5, 'cherry': 3}

Iterating Over a Dictionary

You can iterate over the keys or values in a dictionary using a for loop. Here’s an example:

for key, value in my_dict.items():
    print(key, value)

This will output:

apple 1
banana 5
cherry 3

Dictionary Methods

Dictionaries in Python come with several built-in methods that allow you to manipulate and retrieve data. Some commonly used methods include:

  • get(): Retrieves the value associated with a key. If the key doesn’t exist, it returns None (or a specified default value).
  • keys(): Returns a list of all the keys in the dictionary.
  • values(): Returns a list of all the values in the dictionary.
  • items(): Returns a list of all key-value pairs as tuples.
  • pop(): Removes and returns the value associated with a key.
  • clear(): Removes all items from the dictionary.

The Time Complexity of Dictionary Operations

Dictionaries provide fast lookup and insertion times on average. The time complexity for most operations (such as accessing, inserting, or deleting) is O(1), regardless of the size of the dictionary. This makes dictionaries an efficient choice for storing and retrieving key-value pairs.

In conclusion, a dictionary is a powerful data structure that allows you to efficiently store and retrieve key-value pairs. It provides fast access to values based on their keys and offers useful methods for manipulating and iterating over the data. Understanding dictionaries is essential for any programmer looking to work with complex data structures efficiently.

Happy coding!

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