How To Convert Float To Int In Python

With Python, it’s frequent to run into circumstances when you need to convert a floating-point number to an integer. For use in a loop or conditional expression, you might need to convert a decimal number to a whole number, for instance.

We’ll go over the many ways which will tell you how to change a float to an int in Python in this blog post.

Need to convert a float to integer in python

There can be many situations where we need an answer to the question of how to turn a float to an integer in Python. Some of the common reasons are:

Data Type Matching: We frequently need to match the data types when working with data. Occasionally we may need an integer value but only have a float value. For instance, we might need to convert a float number to an integer value when using indexing or iteration.
Memory Optimization: In certain circumstances, utilising an integer value rather than a float number can conserve memory. When working with enormous datasets, this is extremely helpful.
Mathematical Calculations: In some mathematical calculations, we need to work with integers instead of floats. Converting a float to an integer can help in simplifying the calculations.
Type Casting: Python is a dynamically typed language, which means the type of a variable can be changed during runtime. It allows us to convert a variable from one data type to another.

In summary, there can be many reasons why we may need to convert a float to an integer in Python. Understanding the different approaches to do so can be helpful in different situations.

Different Approaches to convert float to int in python

There are several ways to transform a float to an integer in Python, including:

Using the built-in “int()” function
Using the floor division operator “//”
Using the built-in “round()” function
Using the “math.floor()” function
Using the “math.ceil()” function
Using the “math.trunc()” function

Detailed Explanation:

1. Using the “int()” function:

To change a float into an integer, use the “int()” method. The “int()” function truncates the decimal portion of float values before returning the integer value. Here’s an illustration:

Code:

float_num = 3.14159
int_num = int(float_num)
print(int_num)

Solution:

This code creates a float variable called float_num with a value of 3.14159.
It then uses the int() function to convert the float to an integer, truncating any decimal values and storing the result in a new variable called int_num.
Finally, it prints the value of int_num to the console. Since the original float value was greater than 1, the resulting integer value is 3, the integer part of the original float value.

Output:

2. Using the floor division operator:

You can also use the floor division operator (//) to convert a float to an integer. The floor division operator divides two numbers and rounds down to the nearest integer. Here’s an example:

Code:

float_num = 3.14159
int_num = float_num // 1
print(int_num)

Solution:

The code defines a floating-point number float_num.
It then uses the floor division operator // to divide float_num by 1, effectively rounding it down to the nearest integer.
The resulting integer is assigned to the variable int_num.
Finally, the code prints int_num to the console.

Output:

3.0

3. Using the round() function:

If you want to round a float to the nearest integer before converting it to an integer, you can use the built-in “round()” function. The “round()” function rounds a floating-point number to the nearest integer. Here’s an example:

Code:

float_num = 3.6
#using round() for float to int
int_num = round(float_num)
print(int_num)

Solution:

A variable named float_num is assigned a value of 3.6.
The round() function is called with float_num as its argument.
The round() function returns the nearest integer to float_num, which is 4.
The resulting integer value of 4 is assigned to a variable named int_num.
The value of int_num is printed to the console, which outputs “4”.

Output:

4. Using the “math.floor()” function:

The “math.floor()” function returns the largest integer less than or equal to the given number. Here’s an example:

Code:

import math
float_num = 3.14159
#using math.floor() for float to int
int_num = math.floor(float_num)
print(int_num)

Solution:

This code imports the math module to access the floor() function.
A float number 3.14159 is assigned to a variable called float_num.
The floor() function is used to round down the float number to the nearest integer, and this integer is assigned to a variable called int_num.
The value of int_num is then printed to the console.

Output:

5. Using the “math.ceil()” function:

The “math.ceil()” function returns the smallest integer greater than or equal to the given number. Here’s an example:

Code:

import math
float_num = 3.14159
int_num = math.ceil(float_num)
print(int_num)

Solution:

This code imports the math module, which provides access to various mathematical functions.
It then creates a variable called float_num and assigns it the value 3.14159, a floating-point number.
The code uses the math.ceil() function to round float_num up to the nearest integer, and assigns the result to the variable int_num.
Finally, it prints the value of int_num to the console.

Output:

6. Using the Math.trunc() function:

The Python math module also contains a function named “math.trunc()” that can be used to convert a float to an integer. The “math.trunc()” function simply removes the decimal portion of the provided number without rounding it up or down. It then returns the truncated integer of the value.

Code:

import math

float_num = 3.14159

#using math.trunc() for float to int
int_num = math.trunc(float_num)

print(int_num)

Solution:

This code uses the math module to truncate a floating point number to an integer.
The code first imports the math module.
A floating point number is defined as float_num.
The math.trunc() function is then used to truncate the floating point number to an integer, and the resulting integer is assigned to int_num.
Finally, the code prints the value of int_num to the console.

Output:

Best method out of six?

The int() function is usually regarded as the most efficient method in Python. An integer can be created from a value using the built-in Python function int(). When combined with it, a floating-point value is reduced to the nearest integer. Because it doesn’t require any additional libraries or modules, this approach is simple to comprehend, straightforward, and efficient.

Moreover, Python’s int() function offers the most accurate way to change a float into an integer. In contrast to other operations like math.floor() and math.trunc(), which reduce the float’s precision to the nearest integer, int() always rounds in the opposite direction, to zero. By doing this, you can be sure that int() will always return the integer that is most similar to the original floating-point value.

Using int() also has the benefit of handling edge circumstances like extremely big or extremely small values. For instance, you can see precision or overflow errors if you attempt to convert a float with a very big or tiny exponent using math.floor() or math.trunc(). But, these situations are easily managed by int().

Sample problem:

Problem 1: Write a program that calculates the final cost of a product after applying a discount. The program should take in the original price and discount percentage (as a decimal). It should then calculate the discounted price (original price multiplied by the discount percentage) and round the result to the nearest integer using the int() function.

Code:

original_price = float(input("Enter the original price: "))
discount_percentage = float(input("Enter the discount percentage as a decimal: "))

#calculate discounted price
discounted_price = original_price * discount_percentage
##using int() for float to int
final_price = int(discounted_price)

print("The final price is:", final_price)

Solution:

We start by taking input from the user for the original price of the product and the discount percentage in decimal format.
We then calculate the discounted price by multiplying the original price with the discount percentage.
Since we want the final price to be an integer value, we use the int() function to round the discounted price to the nearest integer.
Finally, we print the calculated final price to the console.

Sample Output:

Enter the original price: 50.0
Enter the discount percentage as a decimal: 0.2
The final price is: 10

Problem 2: Write a program that checks whether a given set of lottery numbers match the winning numbers. The program should take in a list of user-selected numbers (as integers or floating-point numbers) and the winning numbers (also as integers or floating-point numbers). It should then compare the two lists and print out whether the user has won or lost. If the user has won, the program should also print out their prize money (rounded to the nearest integer).

Code:

user_numbers = [23, 17.5, 9.8, 42.6, 11.2]
winning_numbers = [23, 17, 10, 43, 11]

# convert the user numbers to integers using floor division
user_numbers = [int(n) for n in user_numbers]

# compare the two lists to check if the user has won
if user_numbers == winning_numbers:
    print("Congratulations! You have won the lottery!")
    
    # calculate the prize money
    prize_money = 1000000 // len(winning_numbers)
    print("Your prize money is:", prize_money)
else:
    print("Sorry, you did not win the lottery. Better luck next time!")

Solution:

We define two lists, user_numbers and winning_numbers, which represent the user-selected numbers and the winning numbers, respectively.
We use a list comprehension to convert each element in user_numbers to an integer using the floor division operator //. This operator performs integer division and rounds down to the nearest integer.
We compare the two lists using the == operator to check if the user has won.
If the user has won, we print a congratulatory message and calculate the prize money by dividing 1,000,000 (the total prize money) by the number of winning numbers. We use integer division // to ensure that the prize money is rounded down to the nearest integer.
If the user has not won, we print a message indicating that they did not win.

Output:

Sorry, you did not win the lottery. Better luck next time!

Problem 3: Loan Payment Calculator: Write a program that calculates the monthly payment on a loan. The program should take in the total loan amount, interest rate (as a decimal), and loan duration (in months). It should then calculate the monthly payment using the following formula:

monthly_payment = (loan_amount * interest_rate) / (1 – (1 + interest_rate)**(-loan_duration))

Code:

loan_amount = float(input("Enter the total loan amount: "))
interest_rate = float(input("Enter the interest rate (as a decimal): "))
loan_duration = int(input("Enter the loan duration (in months): "))

#calculating monthly payment
monthly_payment = (loan_amount * interest_rate) / (1 - (1 + interest_rate)**(-loan_duration))

#using round() for float to int
rounded_payment = round(monthly_payment)

print("The monthly payment is:", rounded_payment)

Solution:

First, we take input from the user for the loan amount, interest rate, and loan duration using the input() function. We use float() to convert the loan amount and interest rate to decimal numbers, and int() to convert the loan duration to an integer.
Next, we calculate the monthly payment using the formula given in the problem statement.
We round the result to the nearest integer using the round() function.
Finally, we print the monthly payment using print(). We also include a message to indicate what the result represents.

Output:

Enter the total loan amount: 5000
Enter the interest rate (as a decimal): 0.05
Enter the loan duration (in months): 60
The monthly payment is: 94

Problem 4: Write a program that calculates a student’s GPA based on their letter grades. The program should take in a list of letter grades (e.g. ‘A’, ‘B’, ‘C’, etc.) and their corresponding credit values (as floating-point numbers). It should then convert the letter grades to their corresponding GPA values (e.g. ‘A’ = 4.0, ‘B’ = 3.0, etc.) and calculate the overall GPA using the following formula:

GPA = (sum of (credit value * GPA value)) / (sum of credit values)

The program should round the final GPA to the nearest integer using the math.floor() function.

Code:

import math

# Define a function to calculate the GPA
def calculate_gpa(grades, credits):

# Define a dictionary to map letter grades to their corresponding GPA values
    grade_points = {
        'A': 4.0,
        'B': 3.0,
        'C': 2.0,
        'D': 1.0,
        'F': 0.0
    }
    total_credits = sum(credits)
    weighted_gpa = sum([credits[i] * grade_points[grades[i]] for i in range(len(grades))])
    gpa = weighted_gpa / total_credits
    return math.floor(gpa + 0.5)

# Example usage
grades = ['A', 'B', 'C', 'D', 'F']
credits = [3.0, 4.0, 2.0, 3.0, 1.0]
gpa = calculate_gpa(grades, credits)
print("Your GPA is:", gpa)

Solution:

The calculate_gpa() function takes two lists as input – grades and credits. The grades list contains the letter grades (as strings) and the credits list contains the corresponding credit values (as floating-point numbers).
A dictionary called grade_points is created which maps each letter grade to its corresponding GPA value.
The sum() function is used to calculate the total number of credits.
A list comprehension is used to calculate the weighted GPA by multiplying each grade’s credit value with its corresponding GPA value and adding them up.
The final GPA is calculated by dividing the weighted GPA by the total number of credits.
The math.floor() function is used to round the final GPA down to the nearest integer.

Output:

Your GPA is: 2

Problem 5: Write a program that converts temperatures between Celsius and Fahrenheit. The program should take in a temperature value and a unit of measurement (either ‘C’ for Celsius or ‘F’ for Fahrenheit). It should then convert the temperature to the other unit of measurement using the following formulas:

Celsius = (Fahrenheit – 32) * (5/9)

Fahrenheit = Celsius * (9/5) + 32

The program should round the final temperature value to the nearest integer using the math.ceil() function.

Code:

import math

def temp_converter(temp, unit):
    if unit == 'C':
        converted_temp = temp * (9/5) + 32
    elif unit == 'F':
        converted_temp = (temp - 32) * (5/9)
    else:
        print("Invalid unit of measurement. Please enter 'C' for Celsius or 'F' for Fahrenheit.")
        return
    
    return math.ceil(converted_temp)

# example usage
temp_f = temp_converter(25, 'C')
print(temp_f) # Output: 77

temp_c = temp_converter(80, 'F')
print(temp_c) # Output: 27

Solution:

The code defines a function called temp_converter that takes two arguments: temp (a temperature value) and unit (a unit of temperature, either ‘C’ or ‘F’).
The function converts the temperature value from Celsius to Fahrenheit if the unit is ‘C’, or from Fahrenheit to Celsius if the unit is ‘F’.
If an invalid unit is provided, the function prints an error message and returns None.
The function returns the converted temperature value rounded up to the nearest integer using the ceil() method from the math module.
Two example usages of the function are provided, demonstrating how to convert temperatures from Celsius to Fahrenheit and from Fahrenheit to Celsius.

Output:

77
27

Problem 6: Create a program that determines how many pizzas and slices are required for a party. The number of attendees and the approximate quantity of slices that each individual will consume should be factored into the program. The total number of slices necessary and the number of pizzas needed to supply those slices should then be determined (assuming each pizza has 8 slices). The math.trunc() function should be used to use the closest integer when rounding the total number of pizzas.

Code:

import math

# Take input from user
num_people = int(input("How many people are attending the party? "))
slices_per_person = int(input("How many slices of pizza will each person eat? "))

# Calculate total slices needed
total_slices = num_people * slices_per_person

# Calculate number of pizzas needed
num_pizzas = math.ceil(total_slices / 8)

# Print results
print(f"You will need {num_pizzas} pizzas to feed {num_people} people, with each person eating {slices_per_person} slices.")

Solution:

We first import the math module to use the ceil and trunc functions later.
We take input from the user using the input function and convert them to integers using the int function.
We then calculate the total number of slices needed by multiplying the number of people by the slices each person will eat.
We calculate the number of pizzas needed by dividing the total slices by 8 (assuming each pizza has 8 slices) and rounding up to the nearest integer using the ceil function.
We print out the results using the print function with formatted strings.

Output:

How many people are attending the party? 4
How many slices of pizza will each person eat? 4
You will need 2 pizzas to feed 4 people, with each person eating 4 slices.

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Conclusion

In conclusion, converting a float to an integer is a common task in Python, and there are several approaches to achieving this.

In this blog post, we covered the different ways to convert a float to an integer, including using the int() function, math.floor(), math.ceil(), math.trunc(), and bitwise operations. While each method has its advantages and disadvantages, the int() function is generally considered the best approach due to its simplicity, efficiency, and precision.

Ultimately, the choice of method will depend on the specific requirements of your program.

Author:

Sanskar Aggarwal

I have experience in multiple programming languages: C++ , Java , Python, Flutter and good command over Data structure. I take ownership of my work and believe in constant of scaling interested in learning new technology and ready to take up new challenges. Follow: