Python Programs to Calculate Perimeter of Triangle

In this article, we will explore different ways to calculate the Perimeter of a Triangle using Python, with detailed explanations and examples.

What is a Triangle?

A triangle is a three-sided polygon (2D shape) with three edges and three vertices. It is one of the basic shapes in geometry and has several properties that define its angles, sides, and area.

Examples of Triangles in Real Life are Pizza slices, Pyramid structures, Roofs of houses, etc.

Understand the Perimeter of a Triangle

The perimeter of a triangle is the total length around the triangle — in other words, it is the sum of the lengths of its three sides.

Perimeter = a + b + c

Where:

• a, b, and c are the lengths of the triangle’s three sides.
• Units are the same as the sides (e.g., cm, m, inches).

For Example, a triangle has sides of length: a = 5 cm, b = 6 cm, c = 7 cm

Then, perimeter = 5 + 6 + 7= 18 cm

1. How to Calculate Perimeter of Triangle

Code Example

# Get all sides of triangle
side1 = 5
side2 = 6
side3 = 7

# Perimeter Formula
perimeter = side1 + side2 + side3
print("Perimeter of the triangle:", perimeter)Code language: Python (python)

Output:

Perimeter of the triangle: 18

2. Calculate Perimeter of Triangle Using User Inputs

Using the input() function we can ask user to provide values for all three sides of a triangle

Note: As the user inputs are in string format, we must convert them into a float for the calculations.

Code Example

a = float(input("Enter side a: "))
b = float(input("Enter side b: "))
c = float(input("Enter side c: "))

perimeter = a + b + c
print("Perimeter of the triangle:", perimeter)Code language: Python (python)

Output:

Enter side a: 5
Enter side b: 10
Enter side c: 12

Perimeter of the triangle: 27.0

3. Calculate Perimeter of Triangle Using a Function

There are multiple advantages of using a function to calculate the perimeter of a triangle as follows:

• A function allows us to write the calculation once and use it multiple times without repeating code.
• If the formula needs to be updated or changed, a function makes it easy to modify in one place.

In the example below, we calculated the perimeter of two triangles by calling the same function.

Code Example

# Function to calculate perimeter
def triangle_perimeter(a, b, c):
    return a + b + c

# Example usage
p1 = triangle_perimeter(5, 6, 7)
print("Perimeter of the triangle:", p1)

p2 = triangle_perimeter(10, 12, 14)
print("Perimeter of the triangle:", p2)


# Output:
# Perimeter of the triangle: 18
# Perimeter of the triangle: 36Code language: Python (python)

4. Calculate Perimeter of Triangle Using Class (OOP)

Object-Oriented Programming (OOP) is a structured way to write code by creating classes and objects. A class is a blueprint for creating objects, while an object is an instance of a class.

This approach provides better structure, reusability, and maintainability in your code. This approach is highly useful, especially for larger applications where multiple triangles need to be handled efficiently.

The following are the advantages of using OOP to calculate the perimeter of a triangle:

• Extensibility: With OOP, we can easily extend the class to calculate area without affecting the existing structure.
• Reusability: If you need to calculate the perimeter of multiple triangles, you can create multiple objects.

Code Example

# Define a class named Triangle
class Triangle:
    def __init__(self, a, b, c):
        self.a = a
        self.b = b
        self.c = c

    # Method to calculate perimeter
    def calculate_perimeter(self):
        return self.a + self.b + self.c

# Create an object of the Triangle class
triangle1 = Triangle(5, 6, 7)
triangle2 = Triangle(10, 12, 14)

# Call the method to calculate perimeter
p1 = triangle1.calculate_perimeter()
p2 = triangle2.calculate_perimeter()

# Display the perimeter
print("Perimeter of the triangle1:", p1)
print("Perimeter of the triangle2:", p2)


# Output:
# Perimeter of the triangle1: 18
# Perimeter of the triangle2: 36Code language: Python (python)

Explanation:

• Define a Class
  • Define a class named Triangle.
  • The class will store all three sides of the triangle.
• Create a Constructor (__init__ method)
  • The constructor (__init__) initializes the three sides when an object is created.
  • The self keyword refers to the current instance of the class.
• Create a Method to Calculate Perimeter
  • Define a method calculate_perimeter() inside the class.
  • This method returns the perimeter using the formula: perimeter = a + b + c
• Create an Object of the Class
  • Use triangle1 = Triangle(5, 6, 7) to create a triangle with: a = 5, b = 6, c = 7
  • Use triangle1 = Triangle(10, 12, 14) to create a triangle with: a = 10, b = 12, c = 14
• Call the Method to get the Perimeter and print it
  • Use calculate_perimeter() to get the perimeter.
  • Store the result in a variable and display it using print().

5. Calculate Perimeter of Triangle Using Lambda

A lambda function in Python is a small, anonymous function that can have multiple arguments but only one expression, which is evaluated and returned. For a more compact implementation, you can use a lambda function.

A lambda function syntax: lambda arguments: expression

• lambda → Keyword to define the function.
• arguments → Input parameters (like a normal function).
• expression → A single operation that returns a result.

Code Example

triangle_perimeter = lambda a, b, c: a + b + c
print("Perimeter of the triangle:", triangle_perimeter(5, 6, 7))

# Output:
# Perimeter of the triangle: 18Code language: Python (python)

Explanation

• a, b, and c are the input parameters.
• a + b + c is the calculation expression.
• triangle_perimeter is the name to call the anonymous lambda function.

Summary

The article offers a clear and simple way for beginners to understand and implement triangle perimeter calculations in Python, helping them strengthen basic programming and math concepts.