Calculating Average Grades with Python

In this blog post, we will discuss how to use Python to input several grades and calculate their average. This is a common task in many educational and work-related scenarios, and Python’s simplicity and versatility make it an excellent choice for this purpose.

Step 1: Collecting Grades

The first step is to collect the grades that we want to average. We can use Python’s input() function to prompt the user for each grade. Here’s a simple example that collects five grades:

pythongrades = []
for i in range(5):
    grade = input(f"Enter grade {i+1}: ")
    grades.append(float(grade))

In this code, we initialize an empty list called grades to store the grades. Then, we use a for loop to iterate five times, prompting the user for each grade using the input() function. The float() function is used to convert the user’s input (which is a string) into a floating-point number that we can use for calculations.
Step 2: Calculating the Average
Once we have collected all the grades, we can calculate the average by summing them up and dividing by the total number of grades. Here’s how we can do this in Python:
pythontotal = sum(grades)
average = total / len(grades)
print(f"The average grade is: {average}")

In this code, we use the sum() function to calculate the sum of all the grades in the grades list. Then, we divide the sum by the length of the list (i.e., the total number of grades) to get the average. Finally, we print the average using the print() function.
Step 3: Handling Potential Issues
While the above code works well for most cases, there are a few potential issues that we should consider:

Invalid Input: The user may enter something that cannot be converted to a floating-point number (e.g., a letter or a symbol). In this case, the float() function will raise a ValueError exception. We can use a try-except block to catch this exception and prompt the user to enter a valid grade.
Empty Input: The user may accidentally leave the input field blank. In this case, the float() function will also raise a ValueError exception. We can handle this case similarly to invalid input.

Here’s an updated version of the code that handles these potential issues:
pythongrades = []
while len(grades) < 5:
    try:
        grade = input("Enter a grade (or leave blank to finish): ")
        if grade == "":
            break
        grades.append(float(grade))
    except ValueError:
        print("Invalid input. Please enter a valid grade.")

if grades:
    total = sum(grades)
    average = total / len(grades)
    print(f"The average grade is: {average}")
else:
    print("No grades entered.")

In this updated code, we use a while loop instead of a for loop to allow the user to enter grades until they have entered five valid grades or leave the input field blank. We also use a try-except block to catch potential ValueError exceptions and handle them gracefully.
Conclusion
Using Python to calculate the average of several grades is a simple yet powerful task. By collecting the grades using the input() function, converting them to floating-point numbers, and then calculating the average using the sum() and len() functions, we can easily obtain the desired result. By handling potential issues such as invalid or empty input, we can ensure that our code is robust and user-friendly.