In this tutorial, you'll learn about Python variables, how to use them effectively, and practice with clear examples and beginner-friendly exercises.

What is a Variable in Python?

When developing a program, you need to work with many values. To store and manipulate these values, you use variables.

In Python, a variable is a label that you assign a value to. A variable always holds some value.

Example:

message = 'Hello, World!'
print(message)

message = 'Good Bye!'
print(message)

Output:

Hello, World!
Good Bye!

In this example:

  • We create a variable called message.

  • First, it holds the value 'Hello, World!', which is printed.

  • Then we assign a new value 'Good Bye!' to it and print again.

This demonstrates that a variable can store different values during a program's execution.

Creating Variables

To define a variable in Python, use the following syntax:

variable_name = value

The = sign is the assignment operator. It assigns a value to a variable.

Examples:

age = 25
name = 'Anna'
height = 1.68
learning_python = True

We can use those variables like this:

print('Name:', name)
print('Age:', age)
print('Height:', height)
print('Learning Python?', learning_python)

Output:

Name: Anna
Age: 25
Height: 1.68
Learning Python? True

Naming Variables

When naming variables, it’s important to follow both rules and best practices.

Rules:

  • Variable names can contain only letters, digits, and underscores (_).

  • They must begin with a letter or an underscore, not a digit.

  • They cannot contain spaces. Use underscores to separate words.

  • They must not be the same as Python keywords or built-in functions.

Best Practices:

  • Use clear and descriptive names. Example:

student_average = 8.5  # better than "sa" or "x"

  • Use lowercase and separate words with underscores (snake_case).

  • Avoid using the lowercase letter "l" and uppercase "O" because they resemble the digits "1" and "0".

More Examples

Example 1: Future age calculation

current_age = 20
years_ahead = 5
future_age = current_age + years_ahead
print('In', years_ahead, 'years, you will be', future_age)

Example 2: Concatenating strings

first_name = 'Carlos'
last_name = 'Silva'
full_name = first_name + ' ' + last_name
print('Full name:', full_name)

Example 3: Swapping values

x = 10
y = 20
print('Before swap:', x, y)
x, y = y, x
print('After swap:', x, y)

Practice: Assignments and Exercises

Exercise 1:

Create a variable called city and assign the name of your city. Then print:

city = 'Lisbon'
print('I live in', city)

Exercise 2:

Create three variables: product, quantity, and price. Calculate the total and print the result:

product = 'Notebook'
quantity = 4
price = 2.5
total = quantity * price
print('Total cost of', product + ':', total, 'USD')

Exercise 3:

Use variables to store two grades and calculate the average:

grade1 = 7.5
grade2 = 8.0
average = (grade1 + grade2) / 2
print('Final average:', average)

Summary

  • A variable is a label that stores a value, which may change during the program.

  • Use the syntax variable_name = value to create a variable.

  • Variable names should follow Python’s rules and be as descriptive as possible.

  • Practice with real examples helps reinforce your understanding and ability to apply variables in programs.

 

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