解题方法

Python Inheritance Syntax 模板

# Parent class (given in question)
class Parent:
    def __init__(self, attr1, attr2):
        self._attr1 = attr1
        self._attr2 = attr2

    def method(self):
        return f"{self._attr1}, {self._attr2}"

# Child class (you write this)
class Child(Parent):
    def __init__(self, attr1, attr2, attr3):
        super().__init__(attr1, attr2)     # call parent constructor
        self._attr3 = attr3                # new attribute

    def method(self):                      # override
        parent_part = super().method()     # call parent version
        return f"{parent_part}, {self._attr3}"

Step-by-Step

1. Class header — class ChildName(ParentName): with colon
2. Constructor — def __init__(self, all_params_including_parents):
3. super().init() — pass only the parent's parameters (NOT self, NOT child-only params)
4. Child attributes — self._new_attr = param for each new attribute
5. Override method — same name and same parameters as parent
6. super().method() — call parent version if needed (usually for accumulation)
7. Add new logic — append / modify the result for child-specific behaviour

Key Rules

• super().__init__(...) must be the first line in the child constructor
• Constructor parameters include parent parameters plus any new ones
• Overridden method must have exactly the same signature (name + params) as parent
• Use super().method() to call parent's version — do not repeat parent logic manually
• New attributes / methods not in parent are only available on child objects

Common Variations

Variation	Pattern
Parent with default params	super().__init__() with matching defaults
Parent without constructor	Child may not need super().__init__() but still call it for clarity
Chained inheritance	class GrandChild(Child): with super().__init__() through the chain
Read file → create objects	Parse data, use if to decide parent or child constructor