How to Fix Common Python OOP Errors: A Step‑by‑Step Guide

1. Introduction

Hello everyone, I am PiPi. A few days ago, a member of the Python Silver Group asked an object‑oriented programming question, as shown in the screenshot below.

The following image shows the runtime error.

2. Implementation Process

Guidance from a contributor suggested that the issue was caused by repeated string formatting using an f prefix; removing the f resolves the first problem.

After fixing that, a new undefined‑variable error appeared due to incorrect indentation. Adjusting the indentation revealed another bug, where class names were missing when invoking methods.

Similar issues appeared in other parts of the code.

A correct implementation was provided as follows:

class Student(object):
    # Define a Student class
    def __init__(self, name, score):
        # Two attributes: name and score
        self.name = name
        self.score = score

    def set_score(self, score):
        if int(score) >= 0 and int(score) <= 100:
            self.score = score
        else:
            raise(ValueError("Score must be between 0 and 100"))

    # Print each student's name and score
    def print_score(self):
        print("姓名是{}，分数是{}".format(self.name, self.score))

if __name__ == '__main__':
    Mable = Student("Mable", 100)
    Mable.print_score()
    Mable.set_score(90)
    Mable.print_score()
    Mable.set_score(120)
    Mable.print_score()

This resolved the user's issues and reinforced the importance of solid OOP fundamentals.

3. Summary

The article presented a Python OOP problem, analyzed the errors, and provided a complete code solution to help readers overcome similar challenges.