Python Variables

Welcome to your Python learning journey! As a beginner, one of the first things you’ll need to understand is variables. Variables are like labeled boxes where you can store information, such as numbers, text, or other data, to use in your programs. In this blog post, we’ll explore what variables are, why they’re important, and how to use them in Python. Let’s get started!

What Are Variables in Python?

In Python, a variable is a name you give to a piece of data, like a number or a word, so you can use it later in your code. Think of it as a container with a label that holds something, like your name or your age. Variables make it easy to work with data without having to repeat it over and over.

Imagine you’re organizing your backpack. You might put your books in one pocket, your snacks in another, and label each pocket to find things easily. In Python, variables are like those labeled pockets—they store information you can use later in your program. Each variable has a name (the label) and a value (what’s inside).

For example, imagine you want to store someone’s name and use it to print a greeting:

Python

name = "Emma" age = 12 print(name, age) # Prints: Emma 12

name is a variable labeled “name” that holds the text "Emma". age is a variable labeled “age” that holds the number 12.

Invalid Example (trying to use a variable before creating it):

Example

print(my_name) # Error: my_name isn’t created yet!

Variables are like your toy box labels—name them clearly so you know what’s inside!

Why Are Variables Important?

Variables are the building blocks of programming. Here’s why they’re so useful for beginners:

Store Data: Variables let you save data, like numbers or text, to use later in your program.

Make Code Flexible: Instead of hardcoding values, variables let you reuse and update data easily.

Improve Readability: Using meaningful variable names makes your code easier to understand.

Simplify Changes: If you need to update a value, you can change it in one place (the variable) instead of everywhere in your code.

Help with Learning: Variables teach you how Python handles data, which is key to writing more complex programs.

Now, let’s learn how to create and use variables in Python!

How to Create Variables in Python

Creating a variable in Python is super easy. You just need a name for the variable and a value to store in it. Here’s the basic syntax:

Python

variable_name = value

Here, variable_name is the name you choose, and value is the data you want to store. For example:

Python

age = 12 # Stores the number 12 name = "Bob" # Stores the text "Bob" score = 95.5 # Stores a decimal number

In this example, we created three variables: age, name, and score, each holding a different type of data.

Rules for Naming Variables

When choosing names for your variables, you need to follow a few rules:

Allowed Characters: Variable names can include letters (a-z, A-Z), numbers (0-9), and underscores (_), but they cannot start with a number. For example:

• Valid: my_name, score2, total_count
• Invalid: 2score, my-name

No Spaces: Use underscores instead of spaces. For example: first_name, not first name.

Case-Sensitive: Python treats Name and name as different variables.

Avoid Reserved Words: Don’t use Python’s reserved words (like print, for, or if) as variable names.

Tip: Choose descriptive names that explain what the variable stores, like student_name instead of x.

Types of Data Variables Can Hold

Python variables can store different types of data, and you don’t need to specify the type—Python figures it out automatically! Here are some common data types:

• Integers: Whole numbers, like age = 15.
• Floats: Decimal numbers, like height = 5.6.
• Strings: Text, like name = "Alice" (use quotes: " or ').
• Booleans: True or False values, like is_student = True.

Example:

Python

age = 15 # Integer height = 5.6 # Float name = "Alice" # String is_student = True # Boolean

How to Use Variables

Once you’ve created a variable, you can use it in your program. Here are some common ways to use variables:

1. Performing Calculations

Variables can store numbers for math operations:

Python

price = 10 tax = 0.1 total = price + (price * tax) # Calculate total with 10% tax print(total) # Prints 11.0

2. Combining Text

Variables can store text and be combined with other text:

Python

name = "Bob" greeting = "Hello, " + name + "!" print(greeting) # Prints "Hello, Bob!"

3. Assign Multiple Values

Python lets you fill multiple boxes at once, which is like putting toys in several boxes with one move. You can assign different values or the same value to multiple variables.

Valid Example (different values):

Example

apple, banana, orange = 5, 10, 15 # Three variables, three values print(apple, banana, orange) # Prints: 5 10 15

Valid Example (same value):

Example

cat = dog = bird = "pet" # All get the same value print(cat, dog, bird) # Prints: pet pet pet

Invalid Example (wrong number of values):

Example

x, y = 1 # Error: Not enough values for two variables print(x, y)

Assigning multiple values is like handing out candies to friends—make sure there’s enough for everyone!

4. Output Variables

You can show what’s in your variables using print(). It’s like opening your toy box to show your friends what’s inside. But be careful when mixing numbers and text!

Valid Example (using commas):

Example

name = "Zoe" age = 8 print("Hi", name, "you are", age) # Prints: Hi Zoe you are 8

Valid Example (combining with strings):

Example

name = "Zoe" age = 8 print("Hi " + name + ", you are " + str(age) + "!") # Prints: Hi Zoe, you are 8!

Invalid Example (mixing types without conversion):

Example

age = 8 print("Age: " + age) # Error: Can’t mix string and number

Use str() to turn numbers into text, or use commas in print() to keep it simple!

5. Global Variables

A global variable is like a toy box everyone in the house can use—it’s created outside a function and available everywhere. To change it inside a function, you need the global keyword.

Valid Example (accessing a global variable):

Example

toys = 50 # Global variable def count_toys(): print("You have", toys, "toys!") # Uses global variable count_toys() # Prints: You have 50 toys!

Valid Example (modifying a global variable):

Example

toys = 50 # Global variable def add_toys(): global toys # Says we want to change the global variable toys = toys + 10 print("Now you have", toys, "toys!") add_toys() # Prints: Now you have 60 toys! print(toys) # Prints: 60

Invalid Example (trying to modify without global):

Example

toys = 50 def add_toys(): toys = toys + 10 # Error: Python thinks toys is a new variable inside the function print(toys) add_toys()

Global variables are like a shared toy box—use global to change its contents inside a function!

6. Variable Exercises

Let’s have fun practicing variables with these beginner-friendly exercises! Try them out and check your answers.

Exercise 1: Create and Print Variables

Make variables for your favorite animal (text), your age (number), and if you like to code (True/False). Print them in a sentence.

Solution:

Example

""" Stores and prints your favorite things """ animal = "dog" # String: Favorite animal age = 11 # Integer: Your age loves_coding = True # Boolean: Do you like coding? print("I’m", age, "and I love my", animal, "- coding is", loves_coding) # Prints: I’m 11 and I love my dog - coding is True

Invalid Attempt (wrong variable name):

Example

my-animal = "dog" # Error: Dash not allowed in name print(my-animal)

Exercise 2: Assign Multiple Values

Assign three candy amounts to three friends in one line, then print the total.

Solution:

Example

friend1, friend2, friend3 = 5, 7, 3 # Give candies to three friends total_candies = friend1 + friend2 + friend3 print("Total candies:", total_candies) # Prints: Total candies: 15

Invalid Attempt (mismatched values):

Example

friend1, friend2 = 5, 7, 3 # Error: Too many values for two variables print(friend1, friend2)

Exercise 3: Output with Variables

Create variables for a game score and player name, then print a message.

Solution:

Example

player = "Max" score = 200 print(player + " scored " + str(score) + " points!") # Prints: Max scored 200 points!

Invalid Attempt (no conversion):

Example

player = "Max" score = 200 print(player + " scored " + score + " points!") # Error: Can’t mix string and number

7. Updating Variables

You can change a variable’s value by assigning a new one:

Python

score = 100 score = score + 10 # Increase score by 10 print(score) # Prints 110

Tips for Using Variables Effectively

Here are some tips to make your variables awesome:

1. Use Meaningful Names: Choose names that describe the data, like total_price instead of tp.
2. Keep It Simple: Don’t make variable names too long, but ensure they’re clear. For example, student_age is better than the_age_of_the_student_in_years.
3. Use Comments: Add comments to explain what your variables are for, especially if it’s not obvious:
   Python

   # Store the user’s age in years age = 12
4. Avoid Hardcoding: Use variables instead of repeating values:
   Python

   # Bad: Repeating the number 10 print(10 * 1) print(10 * 2) # Good: Using a variable multiplier = 10 print(multiplier * 1) print(multiplier * 2)

Common Mistakes to Avoid

As a beginner, here are some variable-related mistakes to watch out for:

1. Using Invalid Names: Don’t start variable names with numbers or use spaces:
   Python

   # Bad: Invalid variable names 2score = 100 # Starts with a number first name = "Alice" # Contains a space # Good: Valid variable names score = 100 first_name = "Alice"
2. Forgetting to Assign a Value: You must assign a value to a variable before using it, or you’ll get an error:
   Python

   # Bad: Using a variable before assigning print(my_variable) # Error: my_variable is not defined # Good: Assign first, then use my_variable = "Hello" print(my_variable)
3. Mixing Data Types Incorrectly: Be careful when combining different types, like strings and numbers:
   Python

   # Bad: Mixing types causes an error age = 15 print("Age: " + age) # Error: can't concatenate string and integer # Good: Convert the number to a string age = 15 print("Age: " + str(age))

Practice Time!

Let’s try using variables! Below is a simple Python program. Add variables and comments to make it clearer, then check your work.

Program:

Python

print("Enter your name: ") print("Hello, " + input() + "!") print("How old are you? ") print("You are " + input() + " years old.")

Your Task: Rewrite the program using variables for the name and age, and add comments to explain each line. Here’s an example solution:

Python

""" This program asks for the user’s name and age, then prints a personalized greeting. """ name = input("Enter your name: ") # Store the user’s name print("Hello, " + name + "!") # Print a greeting with the name age = input("How old are you? ") # Store the user’s age print("You are " + age + " years old.") # Print the user’s age

Try rewriting the program with variables and compare it to this example. Did you use clear variable names and add helpful comments?

What’s Next?

Congratulations! You now know how to use variables to store and manage data in Python. This is a huge step toward writing real programs! Keep practicing by creating variables for different types of data, like numbers, text, or True/False values. In your next lesson, you might explore operators, conditionals, or loops—variables will be essential for all of them.