Python Programs to check if a number is a Perfect Square

In this article, we’ll explore how to write a Python program to determine whether a given number is a perfect square. This exercise will help you understand mathematical operations and conditional logic in Python.

A Perfect Square is a number that can be expressed as the square of an integer. In other words, if you multiply an integer by itself, the result is called a Perfect Square. For example, 4=2×2, so 4 is a perfect square. Similarly, 9=3×3, so 9 is a perfect square. And so on…

This tutorial covers various methods to check if a number is a perfect square in Python, with explanations and examples.

1. How to check if Number is Perfect Square in Python

Code Example

import math

def is_perfect_sq(num):
    if num < 0:
        return False  # Negative numbers cannot be perfect squares
    sqrt_num = math.sqrt(num)
    return sqrt_num.is_integer()  # Check if the square root is an integer

# Check if it's a perfect square
print(is_perfect_sq(15))    # False
print(is_perfect_sq(36))    # TrueCode language: Python (python)

2. Using math.isqrt function

math.isqrt() is a function in Python’s math module that computes the integer square root of a non-negative integer. It avoids floating-point precision issues by returning an exact integer.

For Example, a Square root of 15 is 3.872983346207417, but math.isqrt(15) returns 3.

This method uses the math.isqrt() function to calculate the square root of a number and check if the integer square root, when squared, equals the original number to determine if it is a perfect square in Python.

For instance, for num = 25, math.isqrt(25) returns 5. Multiplying 5 * 5 results in 25, validating it as a perfect square.

Code Example

import math

# Function to check if a number is a perfect square
def is_perfect_square(num):
    if num < 0:
        return False  # Negative numbers cannot be perfect squares

    sqrt_num = math.isqrt(num)  # Get the integer square root
    is_perfect_sq = sqrt_num * sqrt_num == num  # Verify if the square matches the number
    return is_perfect_sq

# Test cases
print(is_perfect_square(16))  # True
print(is_perfect_square(20))  # FalseCode language: Python (python)

Explanation

• math.isqrt(): Computes the integer square root of a number, avoiding potential floating-point precision errors.
• Validation check: Compute the integer square root using math.isqrt() and multiply it by itself. If the result equals the original number, it confirms that the number is a perfect square.
• math.isqrt() is available from Python 3.8. For earlier versions, use int(math.sqrt(num))

Note:

• Zero is considered a perfect square: 0×0=0
• Negative numbers are never perfect squares because the square of any real number (positive or negative) is non-negative.