Python多边形类实例化报错TypeError：缺失参数x的原因与解决

Let's walk through why you're getting that error and fix up your code to work as intended.

1. Why the TypeError Happens #

The error message TypeError: __init__() missing 1 required positional argument: 'x' spells out exactly what's wrong:

• Your polygon class's constructor method (__init__) is defined to require one parameter x, but when you create an instance with stone = polygon(), you aren't passing any arguments to it.
• Python can't locate the required x value it needs to initialize the class, so it throws this error.

On top of that, your current code has a few other logic inconsistencies we'll address along the way.

2. Key Issues in the Original Code #

Let's list out the other problems to fix:

• The __init__ method has conflicting code: you first assign self.x = x, then immediately overwrite it with self.x = []—this makes the initial x parameter completely useless.
• The __inputSides__ method re-prompts for the number of sides, which defeats the purpose of passing it to the class initially.
• You call stone.__dispSides__(4) with a number, but the method expects a list of side lengths—this would cause a second error once you fix the first one.
• Using double underscores (__method__) for your custom methods is unnecessary here. That naming convention is reserved for Python's built-in special methods (like __init__ or __str__). For your own methods, use single underscores or plain names.

3. Refactored Working Code #

Here's the fixed version with explanations of each change:

class Polygon:
    # Follow PEP8 convention: use PascalCase for class names
    def __init__(self, num_sides):
        # Store the number of sides as an instance attribute
        self.num_sides = num_sides
        # Initialize an empty list to hold side lengths
        self.side_lengths = []

    def input_sides(self):
        # Use the instance's stored num_sides instead of re-prompting
        print(f"Enter {self.num_sides} side lengths:")
        for i in range(self.num_sides):
            length = float(input(f"Side {i+1} length: "))
            self.side_lengths.append(length)

    def display_sides(self):
        # Pull side lengths directly from the instance's attribute
        print("Polygon side lengths:")
        for idx, length in enumerate(self.side_lengths, 1):
            print(f"Side {idx}: {length}")

# Step 1: Get number of sides from the user
num_sides = int(input("Enter number of sides: "))
# Step 2: Create Polygon instance with the required num_sides argument
stone = Polygon(num_sides)
# Step 3: Collect side lengths
stone.input_sides()
# Step 4: Display the collected lengths
stone.display_sides()

What Changed: #

• Renamed the class to Polygon (aligning with Python's style guidelines).
• The __init__ method now properly stores the number of sides and initializes an empty list for side lengths.
• input_sides uses the instance's num_sides value instead of asking again, and saves lengths directly to the instance's side_lengths attribute.
• display_sides reads from the instance's stored lengths, so you don't need to pass a list to it.
• We now create the instance correctly by passing num_sides to Polygon(), matching the __init__ method's requirements.

4. Example Run #

Enter number of sides: 4
Enter 4 side lengths:
Side 1 length: 5
Side 2 length: 5
Side 3 length: 5
Side 4 length: 5
Polygon side lengths:
Side 1: 5.0
Side 2: 5.0
Side 3: 5.0
Side 4: 5.0

内容的提问来源于stack exchange，提问作者John Rawls