Python Variables

« Previous Next »

Python Variables

A variable in Python is used to store information that can be reused later in a program. You can think of it as a label attached to a value, allowing you to refer to that value by name.

Creating Variables in Python

Python does not require any special keyword to create a variable. A variable is automatically created when you assign a value to it for the first time.

Example:

count = 12 username = "Alice" print(count) print(username)

Try it Yourself

In this example, Python determines the type of each variable based on the value assigned to it.

Type Casting

Sometimes, you may want to explicitly convert a value from one data type to another. This process is called type casting.

Example:

num_text = str(45) # Converts number to string num_value = int("20") # Converts string to integer decimal = float(8) # Converts integer to float print(num_text, num_value, decimal)

Try it Yourself

Casting is useful when working with user input or performing calculations.

Checking the Data Type

You can find out the type of any variable by using the built-in type() function.

Example:

price = 99.99 status = "Available" print(type(price)) print(type(status))

Try it Yourself

This helps in debugging and understanding how data is handled in your program.

Using Single or Double Quotes

Strings in Python can be written using either single quotes (' ') or double quotes (" "). Both formats work exactly the same way.

Example:

city = "Chennai" language = 'Python'

Try it Yourself

Choose one style and use it consistently in your code.

Case Sensitivity in Variable Names

Python treats uppercase and lowercase letters as different. This means variable names that look similar but differ in case are considered separate variables.

Example:

score = 85 Score = "Excellent" print(score) print(Score)

Try it Yourself

Here, score and Score are two distinct variables, and one does not affect the other.

Naming Variables in Python

In Python, variable names can be very short (such as i or n) or more meaningful and descriptive (like student_age, total_marks, or file_count). Using clear names makes your code easier to understand and maintain.

Rules for Valid Variable Names

Python follows strict rules when naming variables:

• A variable name must begin with a letter (a–z, A–Z) or an underscore (_)
• It must not start with a number
• Only letters, numbers, and underscores are allowed
• Variable names are case-sensitive
• Python keywords (such as for, if, class) cannot be used as variable names

Examples of Valid Variable Names

The following variable names follow all Python naming rules:

suser = "Ravi" user_name = "Ravi" _user_id = 101 userName = "Ravi" USERNAME = "Ravi" user2 = "Ravi"

Try it Yourself

Examples of Invalid Variable Names

The variable names below will cause errors because they break Python’s naming rules:

3user = "Ravi" # Cannot start with a number user-name = "Ravi" # Hyphens are not allowed user name = "Ravi" # Spaces are not allowed

Try it Yourself

Naming Variables with Multiple Words

When a variable name contains more than one word, it’s important to format it in a readable way. Python developers commonly use the following naming styles:

Camel Case

The first word starts with a lowercase letter, and each following word begins with an uppercase letter.

totalPriceAmount = 2500

Try it Yourself

Pascal Case

Every word in the variable name starts with a capital letter.

TotalPriceAmount = 2500

Try it Yourself

Snake Case

All words are lowercase and separated using underscores.

This is the most recommended style in Python.

total_price_amount = 2500

Try it Yourself

Using meaningful variable names and consistent naming styles greatly improves code readability and professionalism.

Assigning Multiple Values to Variables in Python

Python allows you to assign multiple values to multiple variables at the same time using a single statement. Each variable receives the value in the corresponding position.

Example:

a, b, c = 10, 20, 30 print(a) print(b) print(c)

Try it Yourself

⚠️ Important: The number of variables must exactly match the number of values. Otherwise, Python will raise a ValueError.

Assigning the Same Value to Multiple Variables

You can also assign one value to several variables at once. This is useful when multiple variables should start with the same initial value.

Example:

x = y = z = 100 print(x) print(y) print(z)

Try it Yourself

All three variables now refer to the same value.

Unpacking a Collection into Variables

Unpacking allows you to take values from a collection—such as a list or tuple—and assign them to individual variables in one step.

Unpacking a List

When unpacking, the number of variables must match the number of items in the collection.

Example:

colors = ["red", "green", "blue"] first, second, third = colors print(first) print(second) print(third)

Try it Yourself

This technique makes your code cleaner and eliminates the need to access elements using indexes.

Displaying Variables in Python

The print() function is commonly used to display the value stored in a variable.

Example:

message = "Learning Python is fun" print(message)

Try it Yourself

This prints the value assigned to the variable on the screen.

Printing Multiple Variables Together

You can display more than one variable in a single print() statement by separating them with commas. Python automatically adds spaces between the values.

Example:

word1 = "Coding" word2 = "with" word3 = "Python" print(word1, word2, word3)

Try it Yourself

This method is simple and works well with different data types.

Using the + Operator with Strings

The + operator can be used to join (concatenate) string values together. When doing this, you must manually include spaces where needed.

Example:

a = "Python " b = "makes " c = "sense" print(a + b + c)

Try it Yourself

If spaces are not added inside the strings, the output will appear merged without gaps.

Using + with Numbers

When used with numeric values, the + operator performs addition instead of concatenation.

Example:

num1 = 15 num2 = 25 print(num1 + num2)

Try it Yourself

The result displayed is the sum of the two numbers.

Mixing Strings and Numbers

Python does not allow you to combine a string and a number using the + operator directly. Doing so results in a type error.

Incorrect Example:

age = 30 name = "Rahul" print(age + name)

Try it Yourself

This causes an error because Python cannot automatically convert between different data types.

Recommended Way to Print Mixed Data

The safest and easiest way to print multiple variables—especially when they contain different data types—is to separate them with commas inside the print() function.

Example:

roll_no = 12 student_name = "Rahul" print(roll_no, student_name)

Try it Yourself

Python automatically handles the formatting, making this approach ideal for beginners.

Global Variables in Python

A global variable is a variable that is created outside of any function. Once defined, it can be accessed from anywhere in the program, including inside functions.

Global variables are useful when multiple parts of a program need to share the same data.

Creating and Using a Global Variable

When a variable is declared outside a function, it automatically becomes global.

Example:

site_name = "GoCourse" def show_site(): print(site_name) show_site()

Try it Yourself

In this example, the function can access site_name even though it was not created inside the function.

Global vs Local Variables

A variable created inside a function is called a local variable. Local variables can only be used within that function.

Example:

language = "Python" def display_language(): language = "Java" print(language) display_language() print(language)

Output:

Java Python

Try it Yourself

Here:

• language inside the function is a local variable
• language outside the function is a global variable
• They are treated as separate variables

Using the global Keyword

If you want to modify a global variable inside a function, you must use the global keyword. Without it, Python will create a new local variable instead.

Example:

count = 1 def increase_count(): global count count += 1 increase_count() print(count)

Try it Yourself

The global keyword tells Python to use the variable defined outside the function.

Creating a Global Variable Inside a Function

You can also create a global variable from inside a function by using the global keyword.

Example:

def set_status(): global status status = "Active" set_status() print(status)

Try it Yourself

After the function runs, status becomes available throughout the program.

Best Practices for Global Variables

• Use global variables sparingly
• Prefer passing values as function arguments
• Avoid modifying global variables unnecessarily
• Use clear and meaningful names for globals

Overusing global variables can make programs harder to debug and maintain.

« Previous Next »