How to Check If a Variable Is a Float in Python

Introduction

In this lab, you will learn how to check if a variable is a float in Python. The lab begins by introducing floating-point numbers and their importance in representing real numbers with decimal points.

You'll start by creating a floats.py file and assigning floating-point values to variables like pi, gravity, and temperature. You'll then perform basic arithmetic operations such as addition, subtraction, multiplication, and division with these variables, observing the results. Finally, the lab will guide you through methods to determine if a variable is indeed a float using type() and isinstance().

Skills Graph

Learn About Floating-Point Numbers

In this step, you will learn about floating-point numbers in Python. Floating-point numbers are used to represent real numbers, which include numbers with decimal points. Understanding how to work with floating-point numbers is crucial for many types of calculations.

Let's start by creating a Python file to experiment with floating-point numbers.

1. Open the VS Code editor in the LabEx environment.
2. Create a new file named floats.py in the ~/project directory.

Now, let's add some code to floats.py:

## Assigning floating-point numbers to variables
pi = 3.14159
gravity = 9.8
temperature = 25.5

## Printing the values
print("Pi:", pi)
print("Gravity:", gravity)
print("Temperature:", temperature)

In this code, we've assigned floating-point values to three variables: pi, gravity, and temperature. The print() function is then used to display these values.

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

python floats.py

You should see the following output:

Pi: 3.14159
Gravity: 9.8
Temperature: 25.5

Now, let's perform some basic arithmetic operations with floating-point numbers:

## Addition
result_addition = pi + gravity
print("Addition:", result_addition)

## Subtraction
result_subtraction = gravity - temperature
print("Subtraction:", result_subtraction)

## Multiplication
result_multiplication = pi * temperature
print("Multiplication:", result_multiplication)

## Division
result_division = gravity / 2
print("Division:", result_division)

Add these lines to your floats.py file and run it again:

python floats.py

You should see output similar to this:

Pi: 3.14159
Gravity: 9.8
Temperature: 25.5
Addition: 12.94159
Subtraction: -15.7
Multiplication: 80.110545
Division: 4.9

Floating-point numbers can also be expressed using scientific notation:

## Scientific notation
avogadro = 6.022e23
print("Avogadro's number:", avogadro)

Add this to your floats.py file and run it:

python floats.py

The output will be:

Pi: 3.14159
Gravity: 9.8
Temperature: 25.5
Addition: 12.94159
Subtraction: -15.7
Multiplication: 80.110545
Division: 4.9
Avogadro's number: 6.022e+23

This demonstrates how to define and use floating-point numbers in Python, including basic arithmetic operations and scientific notation.

Check with type()

In this step, you will learn how to use the type() function in Python to determine the data type of a variable. This is particularly useful when you're working with different types of numbers and want to ensure you're performing the correct operations.

Let's continue working with the floats.py file you created in the previous step. We'll add code to check the type of our floating-point variables.

1. Open the floats.py file in the VS Code editor.

2. Add the following code to the end of the file:

## Checking the type of variables
print("Type of pi:", type(pi))
print("Type of gravity:", type(gravity))
print("Type of temperature:", type(temperature))

## Checking the type of the result of addition
print("Type of result_addition:", type(result_addition))

In this code, we're using the type() function to determine the data type of the variables pi, gravity, temperature, and result_addition. The print() function then displays the data type.

Now, run the script:

python floats.py

You should see output similar to this:

Pi: 3.14159
Gravity: 9.8
Temperature: 25.5
Addition: 12.94159
Subtraction: -15.7
Multiplication: 80.110545
Division: 4.9
Avogadro's number: 6.022e+23
Type of pi: <class 'float'>
Type of gravity: <class 'float'>
Type of temperature: <class 'float'>
Type of result_addition: <class 'float'>

As you can see, the type() function confirms that all these variables are of the float type.

Now, let's see what happens if we have an integer:

## Integer variable
integer_number = 10
print("Type of integer_number:", type(integer_number))

Add this to your floats.py file and run it:

python floats.py

The output will now include:

Pi: 3.14159
Gravity: 9.8
Temperature: 25.5
Addition: 12.94159
Subtraction: -15.7
Multiplication: 80.110545
Division: 4.9
Avogadro's number: 6.022e+23
Type of pi: <class 'float'>
Type of gravity: <class 'float'>
Type of temperature: <class 'float'>
Type of result_addition: <class 'float'>
Type of integer_number: <class 'int'>

This shows that integer_number is of the int type. The type() function is a useful tool for understanding the data types you're working with in Python.

Use isinstance() for Floats

In this step, you will learn how to use the isinstance() function in Python to check if a variable is of a specific type. This is a more robust way to check data types compared to using type() directly, especially when dealing with inheritance and complex type hierarchies.

Let's continue working with the floats.py file you've been using in the previous steps.

1. Open the floats.py file in the VS Code editor.

2. Add the following code to the end of the file:

## Checking if a variable is a float using isinstance()
print("Is pi a float?", isinstance(pi, float))
print("Is gravity a float?", isinstance(gravity, float))
print("Is temperature a float?", isinstance(temperature, float))

## Checking if a variable is an integer using isinstance()
print("Is integer_number an integer?", isinstance(integer_number, int))

## Checking if a variable is a number (int or float)
print("Is pi a number?", isinstance(pi, (int, float)))
print("Is integer_number a number?", isinstance(integer_number, (int, float)))

In this code, we're using the isinstance() function to check if the variables pi, gravity, temperature, and integer_number are of the float or int type. The isinstance() function takes two arguments: the variable to check and the type (or a tuple of types) to check against. It returns True if the variable is of the specified type, and False otherwise.

Now, run the script:

python floats.py

You should see output similar to this:

Pi: 3.14159
Gravity: 9.8
Temperature: 25.5
Addition: 12.94159
Subtraction: -15.7
Multiplication: 80.110545
Division: 4.9
Avogadro's number: 6.022e+23
Type of pi: <class 'float'>
Type of gravity: <class 'float'>
Type of temperature: <class 'float'>
Type of result_addition: <class 'float'>
Type of integer_number: <class 'int'>
Is pi a float? True
Is gravity a float? True
Is temperature a float? True
Is integer_number an integer? True
Is pi a number? True
Is integer_number a number? True

As you can see, isinstance() correctly identifies the data types of the variables. It also demonstrates how to check if a variable is one of several types by passing a tuple of types as the second argument. This is a powerful tool for writing flexible and robust code that can handle different types of input.

Summary

In this lab, you learned about floating-point numbers in Python, which represent real numbers with decimal points. You created a floats.py file to experiment with assigning floating-point values to variables like pi, gravity, and temperature, and then printed these values.

The lab also covered basic arithmetic operations with floating-point numbers, including addition, subtraction, multiplication, and division. You executed the floats.py script to observe the results of these operations.