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It is a common practice for educational institutions to evaluate students based on their performance through grading. This tutorial aims to help you understand a Python program that inputs a student's marks and displays the corresponding grade based on the marks obtained.

Understanding the Grading System

A grading system is a method of evaluating students' performance based on their marks. The system usually divides the entire range of possible marks into segments, with each section representing a specific grade. For instance, marks could be translated into grades as follows:

  • A: 90 and above
  • B: between 80 and 89
  • C: between 70 and 79
  • D: between 60 and 69
  • F: below 60

Implementing the Grading System in Python

The program compares students' marks against predefined grade ranges. Here's how you can implement it:

  1. Input Marks: Start by taking the student's marks as input.
  2. Determine Grade: Use if-else statements to compare the marks against the grade boundaries and assign the corresponding grade.
  3. Display Grade: Finally, display the grade to the user.

Code Example

Below is a simple Python program illustrating the above logic:

    marks = float(input("Please enter the marks (0-100): "))
    # Validate the marks are within a plausible range (0-100)
    if 0 <= marks <= 100:
        if marks >= 90:
            grade = 'A'
        elif marks >= 80:
            grade = 'B'
        elif marks >= 70:
            grade = 'C'
        elif marks >= 60:
            grade = 'D'
            grade = 'F'
        print("Grade:", grade)
        print("Invalid marks. Please enter a value between 0 and 100.")
except ValueError:
    print("Invalid input. Please enter a numeric value.")


$ python
Please enter the marks (0-100): 81
Grade: B

In the program above, we start by taking the marks as input and converting them into a float data type for accurate grade calculation. Next, the program validates if the entered marks fall within the acceptable range of 0-100. After validation, if-elif-else statements compare the marks against the grade thresholds and assign the appropriate grade based on the entered marks. Finally, the program displays the grade. If the input is not a valid numeric value or falls outside the acceptable range, the program outputs the input error and prompts to enter the correct data.


This Python program provides an example of using conditional statements to solve a common problem - grading students based on their marks. Knowing how to apply such logic is essential for beginners in Python programming. It serves as the basis for more complex decision-making in software development. Perfecting these fundamental concepts enables you to tackle more intricate programming challenges and implement them in real-world situations.

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