A Guide to Lists and Data Structures in Python

3 min readSep 16, 2023

Written by — Divyansh Gupta (AI/ML TEAM IOSC)

Introduction

Data structures in Python are fundamental constructs that allow you to organize, store, and manipulate data efficiently. Python offers several built-in data structures, and you can also implement custom data structures to suit your specific needs. In this guide, we’ll explore the most common built-in data structures in Python and provide essential commands and operations for each of them.

Lists

Lists are ordered collections of items in Python. They are mutable, meaning you can change their content after creation. Lists can contain elements of different data types.

my_list = [1, 2, 3, "Python", True]

Command Snippets for Lists:

Creating Lists:

my_list = [1, 2, 3, 4, 5]

2. Accessing Elements:

first_element = my_list[0] last_element = my_list[-1]

3. Slicing Lists:

sliced_list = my_list[1:4]  # Creates a new list [2, 3, 4]

4. Modifying Lists:

my_list.append(6) # Add an element to the end
my_list.insert(2, 10) # Insert element at a specific index
my_list.remove(3) # Remove the first occurrence of a value
my_list.pop(2) # Remove and return element at a specific index
my_list.extend([7, 8, 9]) # Extend the list with another list

5. List Comprehensions:

squares = [x**2 for x in my_list]

6. Sorting:

sorted_list = sorted(my_list) # Creates a sorted copy
my_list.sort() # Sorts the list in-place

Tuples

Tuples are similar to lists but are immutable, meaning their content cannot be modified after creation. They are often used for grouping related data together.

my_tuple = (1, 2, 3, "Python", True)

Command Snippets for Tuples:

Creating Tuples:

my_tuple = (1, 2, 3, 4, 5)

2. Accessing Elements:

first_element = my_tuple[0] last_element = my_tuple[-1]

3. Tuples are Immutable:

Attempting to modify a tuple will result in a TypeError.

Strings

Strings in Python are sequences of characters. They are immutable, meaning you cannot change individual characters in a string.

my_string = "Hello, World!"

Command Snippets for Strings:

Creating Strings:

my_string = "Hello, World!"

2. Accessing Characters:

first_char = my_string[0]

3. String Slicing:

substring = my_string[7:12]  # Creates a substring "World"

4. String Concatenation:

new_string = my_string + " Welcome"

5. String Methods:

length = len(my_string) # Get the length of the string
uppercase = my_string.upper() # Convert to uppercase
lowercase = my_string.lower() # Convert to lowercase

6. String Formatting:

name = "Alice" age = 30 formatted_string = f"My name is {name} and I am {age} years old."

Dictionaries

Dictionaries are collections of key-value pairs in Python. They are unordered and use keys to access values. Keys must be unique and immutable (strings, numbers, or tuples).

my_dict = {"name": "John", "age": 30, "city": "New York"}

Command Snippets for Dictionaries:

Creating Dictionaries:

my_dict = {"name": "John", "age": 30, "city": "New York"}

2. Accessing Values:

name = my_dict["name"]

3. Modifying Dictionaries:

my_dict["job"] = "Engineer" # Add a new key-value pair
del my_dict["age"] # Remove a key-value pair

4. Dictionary Methods:

keys = my_dict.keys() # Get all keys as a list
values = my_dict.values() # Get all values as a list
items = my_dict.items() # Get key-value pairs as tuples

5. Checking Key Existence:

if "name" in my_dict:     # Do something

Conclusion

In this guide, we’ve explored the fundamental data structures in Python — lists, tuples, strings, and dictionaries. These versatile tools empower Python developers to manage and manipulate data efficiently, whether it’s organizing information, performing complex operations, or crafting elegant code. By mastering these data structures and their associated commands, you’ll be better equipped to tackle a wide range of programming challenges. As you continue your Python journey, remember that practice is key to becoming proficient. So, dive into coding, experiment with these data structures, and unlock the full potential of Python for your projects. Happy coding!