Python Dictionaries (With Examples) : A Comprehensive Tutorial

Python Dictionaries (With Examples) : A Comprehensive Tutorial

08 Jul 2024
Intermediate
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12 min read

Dictionary in Python: An Overview

Are you looking to become adept in the Python language? Do you want to fast-track your mastery of the language by diving into its core components, like dictionaries? Then you may want to get into a Python Certification Course. In this Python Tutorial, we will explain what exactly a dictionary is in Python programming as well as some tips and tricks on working with it effectively.

What is a dictionary in Python?

A dictionary in Python is a group of key-value pairs, sometimes referred to as a hash table. Every key is distinct and corresponds to a single value. Dictionary entries can have their values modified after they are created, which is known as mutability. Data is organized and stored using dictionaries. They can be used to store object-specific information such as attributes and methods.

Dictionary in Python

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Creating a Dictionary in Python

In Python, creating a dictionary is a simple procedure. Two techniques to create a dictionary are as follows:

  1. Using curly braces
  2. Using the dict() function

1. Using curly braces

Curly braces {} are used in this method to define the dictionary. You specify key-value pairs, separated by commas, inside the curly braces. The data you wish to save is the value, and the key serves as the value's identification.

Example of Creating Dictionary using Curly Braces in Python Editor

  country_capitals = {"France": "Paris", "Germany": "Berlin", "Italy": "Rome"}
print(country_capitals)

Output

{'France': 'Paris', 'Germany': 'Berlin', 'Italy': 'Rome'}
2. Using the dict() function

Using the built-in dict() function, you create the dictionary in this method. Key-value pairs are the only argument accepted by the function.

Example of Creating Dictionary using dict() Function in Python

        country_capitals = dict([("France", "Paris"), ("Germany", "Berlin"), ("Italy", "Rome")])
print(country_capitals)

Output

{'France': 'Paris', 'Germany': 'Berlin', 'Italy': 'Rome'}

Access Value in Dictionary in Python

  • To access the objects in a dictionary, use its key name.
  • You can use the key inside square brackets.
  • The element can also be accessed from a dictionary with the help of a Python function named get().
  • This function returns the value after accepting the key as an input.

Example of Accessing Values in Dictionary in Python

        dictionary = {"name": "Mohan Kumar", "age": 35, "city": "New Delhi"}
name = dictionary["name"]
print(name)  
The dictionary containing personal data is defined in the code. The value related to the 'name' key is then retrieved and printed from the dictionary.

Output

Mohan Kumar

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Adding elements to a Dictionary

  • In Python, the assignment operator (=) is the most popular and straightforward way to add elements to a dictionary.
  • This method includes directly assigning the required value to the specified key within the dictionary.

Example of Adding Elements to a Dictionary in Python

        student_info = {}
student_info["name"] = "Mohan Kumar"
student_info["age"] = 35
print(student_info)

The code first generates an empty dictionary called "student_info," adds key-value pairs for "name" and "age," and then prints the student's information from the dictionary.

Output

{'name': 'Mohan Kumar', 'age': 35}

Update Dictionary in Python

  • The most popular and effective approach to updating a dictionary is using the update() method.
  • It updates the dictionary with key-value pairs that are passed in as an iterable object.
  • A key's value is rewritten if it is already in the dictionary.
  • A new key-value pair is added to the dictionary if a key is missing.

Example of Updating Dictionary in Python

        dictionary = {'name': 'Mohan Kumar', 'age': 35, 'city': 'New Delhi'}
update_data = {'age': 32, 'country': 'India'}
dictionary.update(update_data)
print(dictionary)

A dictionary is initialized with personal data by the code. The 'age' property is then updated, and a new 'country' key with matching values is added. It prints the updated dictionary at the end.

Output

{'name': 'Mohan Kumar', 'age': 32, 'city': 'New Delhi', 'country': 'India'}

Delete Dictionary Elements in Python

  • In Python, deleting dictionary elements involves removing specific key-value pairs from the dictionary.
  • The specified key-value pair is immediately deleted from the dictionary by using the del keyword.
  • If the given key is not present in the dictionary, a KeyError is raised.

Example of Deleting Dictionary Elements in Python Compiler

        dictionary = {"a": 1, "b": 2, "c": 3}
del dictionary["b"] 
print(dictionary) 

Output

{'a': 1, 'c': 3}

Built-in Dictionary Functions

Sr.No. Function Description
1 cmp(dict1, dict2) Compares elements of both dict.
2 len(dict) Gives the total length of the dictionary which would be equal to the number of items in the dictionary
3 str(dict) Produces a printable string representation for that dictionary
4type(variable) Returns the type of the passed variable. If there is a passed variable in a dictionary, then it would return a dictionary type.

Built-in Dictionary methods

Sr.No. Methods Description
1dict.clear() Removes all elements of dictionary dict
2 dict.copy()Returns a shallow copy of dictionary dict
3dict.fromkeys()Create a new dictionary with keys from seq and values set to value.
4 dict.get(key, default=None) For "key" key, returns value or default if the key is not in the dictionary
5dict.has_key(key)Returns true if key in dictionary dict, false otherwise
6dict.items()Returns a list of dict's (key, value) tuple pairs
7dict.keys()Returns list of dictionary dict's keys
8dict.setdefault(key, default=None)Similar to get(), but will set dict[key]=default if "key" is not already in dict
9dict.update(dict2) Adds dictionary dict2's key-values pairs to dict
10dict.values() Returns list of dictionary dict's values
Summary
Dictionaries in Python are useful tools for storing and organizing data. They are necessary for Python programming since they make data access and manipulation efficient. With this newfound knowledge, you can now start building incredible projects utilizing Python dictionaries effectively. Enhance your skills with a Python training program.

FAQs

Q1. How do I make a dictionary in Python?

In Python, there are two ways to generate a dictionary. The first method is to utilize empty curly brackets {}. The second method is using the dict() function.

Q2. How can I add key-value pairs to a dictionary?

The assignment operator = can be used to add key-value pairs to a dictionary.

Q3. How can I access the values in a dictionary?

The square brackets [] with the key as the index can be used to access values in a dictionary.
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Sakshi Dhameja (Author and Mentor)

She is passionate about different technologies like JavaScript, React, HTML, CSS, Node.js etc. and likes to share knowledge with the developer community. She holds strong learning skills in keeping herself updated with the changing technologies in her area as well as other technologies like Core Java, Python and Cloud.

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