How to Check If a Variable Is an Integer in Python

Introduction

In this lab, you will learn how to check if a variable is an integer in Python. We'll start by understanding the fundamental data type of integers, which are whole numbers without decimal points, and how to declare and use integer variables.

Then, you'll explore the type() function to identify the data type of a variable and the isinstance() function to confirm if a variable is an integer. This will equip you with the tools to effectively work with integers and ensure you're performing the correct operations in your Python code.

Skills Graph

Understand Integers

In this step, we will explore integers, one of the fundamental data types in Python. Integers are whole numbers, which can be positive, negative, or zero, without any decimal points. Understanding integers is crucial for performing mathematical operations and working with numerical data in Python.

Let's start by creating a Python file named integers.py in your ~/project directory using the VS Code editor.

~/project/integers.py

Now, open integers.py in the editor and add the following lines of code:

## Assigning integer values to variables
x = 10
y = -5
z = 0

## Printing the values of the variables
print("The value of x is:", x)
print("The value of y is:", y)
print("The value of z is:", z)

In this code, we've assigned integer values to three variables: x, y, and z. x is assigned a positive integer (10), y is assigned a negative integer (-5), and z is assigned zero (0). The print() function is then used to display the values of these variables.

To run the script, open your terminal in VS Code (you can usually find it under "View" -> "Terminal") and execute the following command:

python integers.py

You should see the following output:

The value of x is: 10
The value of y is: -5
The value of z is: 0

This demonstrates how to declare and use integer variables in Python. Integers are used extensively in various programming tasks, such as counting, indexing, and performing calculations.

Use type() to Identify Integers

In this step, we will learn how to use the type() function in Python to identify the data type of a variable. The type() function is a built-in function that returns the type of an object. This is particularly useful when you're working with different data types and need to ensure that you're performing the correct operations.

Let's modify the integers.py file we created in the previous step to include the type() function. Open integers.py in the VS Code editor and add the following lines of code:

## Assigning integer values to variables
x = 10
y = -5
z = 0

## Printing the values of the variables
print("The value of x is:", x)
print("The value of y is:", y)
print("The value of z is:", z)

## Using the type() function to identify the data type
print("The type of x is:", type(x))
print("The type of y is:", type(y))
print("The type of z is:", type(z))

Here, we've added three new print() statements that use the type() function to determine the data type of the variables x, y, and z.

Now, run the script again using the following command in the terminal:

python integers.py

You should see the following output:

The value of x is: 10
The value of y is: -5
The value of z is: 0
The type of x is: <class 'int'>
The type of y is: <class 'int'>
The type of z is: <class 'int'>

As you can see, the type() function confirms that x, y, and z are all of the int (integer) type. This is a simple yet powerful way to verify the data types of your variables in Python.

Confirm with isinstance()

In this step, we will explore the isinstance() function in Python, which provides another way to verify the data type of a variable. The isinstance() function checks if an object is an instance of a specified class or type. This is particularly useful for more complex type checking scenarios.

Let's continue modifying the integers.py file. Open integers.py in the VS Code editor and add the following lines of code:

## Assigning integer values to variables
x = 10
y = -5
z = 0

## Printing the values of the variables
print("The value of x is:", x)
print("The value of y is:", y)
print("The value of z is:", z)

## Using the type() function to identify the data type
print("The type of x is:", type(x))
print("The type of y is:", type(y))
print("The type of z is:", type(z))

## Using isinstance() to confirm the data type
print("Is x an integer?", isinstance(x, int))
print("Is y an integer?", isinstance(y, int))
print("Is z an integer?", isinstance(z, int))

In this code, we've added three new print() statements that use the isinstance() function to check if the variables x, y, and z are instances of the int class. The isinstance() function returns True if the object is an instance of the specified class, and False otherwise.

Now, run the script again using the following command in the terminal:

python integers.py

You should see the following output:

The value of x is: 10
The value of y is: -5
The value of z is: 0
The type of x is: <class 'int'>
The type of y is: <class 'int'>
The type of z is: <class 'int'>
Is x an integer? True
Is y an integer? True
Is z an integer? True

The isinstance() function confirms that x, y, and z are indeed integers. This method is often preferred over type() for its flexibility, especially when dealing with inheritance and polymorphism.

Summary

In this lab, we began by exploring integers in Python, understanding that they are whole numbers (positive, negative, or zero) without decimal points. We created a integers.py file, assigned integer values to variables x, y, and z, and then printed these values to the console, demonstrating the declaration and usage of integer variables.

Next, we learned how to use the type() function to identify the data type of a variable. This built-in function returns the type of an object, which is useful for ensuring correct operations when working with different data types.