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考前速记

Inheritance Quick Template​

class Child(Parent):
    def __init__(self, p1, p2, c1):          # all params including parent's
        super().__init__(p1, p2)             # 1st line — call parent
        self._c1 = c1                        # child-specific attributes

    def override_method(self):
        base = super().override_method()     # reuse parent behaviour
        return base + child_extra            # extend it

5-Step Checklist​

  • 1. class Child(Parent): — colon at end
  • 2. def __init__(self, ...): — include ALL parent params + new ones
  • 3. super().__init__(...) — only parent params, NO self
  • 4. self._new_attr = value — initialise each new attribute
  • 5. Override method — exact same signature, super().method() if needed

File + Inheritance Pattern​

def load(filename):
    items = []
    with open(filename) as f:
        for line in f:
            data = line.strip().split(",")
            if data[0] == "P":
                items.append(Parent(data[1], data[2]))
            else:
                items.append(Child(data[1], data[2], data[3]))
    return items

Common Traps — Last Look​

TrapFix
super().__init__(self, ...)Remove self
Wrong param order in super().__init__Match parent exactly
Missing colon on class headerAdd :
Override with different paramsMatch parent signature
Not converting int() from fileWrap numeric fields
Object created inside if lostUse list.append()

Polymorphism in One Line​

for obj in [Parent("a", 1), Child("b", 2, 3)]:
    print(obj.method())            # different output for each