90-94 到二叉樹了 不是很會寫這個資料結構
阿新 • • 發佈:2021-11-20
繼承(重要)
1. 什麼是繼承?
# 繼承就是新建類的一種方式,新建的類我們稱為子類或者叫派生類,被繼承的類我們稱為父類或者基類
# 子類可以使用父類中的屬性或者方法
2. 為什麼要用繼承?
類解決了物件與物件之間的程式碼冗餘問題
繼承解決的是類與類之間的程式碼冗餘問題
3. 如何使用繼承?
新式類:繼承了object類的子子孫孫類都是新式類
經典類:沒有繼承了object類的子子孫孫類都是經典類
# 新式類和經典類只有在python2中區分
類的繼承
# 以學生選課系統為例 # 父類,公共類 class People(): school = 'SH' def __init__(self, name, age, gender): self.name = name self.age = age self.gender = gender # 學生類 class Student(People): def __init__(self, name, age, gender, course=None): if course is None: course = [] People.__init__(self, name, age, gender) self.courses = course def choose_course(self, course): self.courses.append(course) print('%s 選課成功 %s' % (self.name, self.courses)) stu = Student('ly', 19, 'male') # teacher類 class Teacher(People): def __init__(self, name, age, gender, level): self.level = level People.__init__(self, name, age, gender) def score(self, stu_obj, score): stu_obj.score = score # 給學生打分 print('%s給%s打了%s分' % (self.name, stu_obj.name, score)) tea = Teacher('ly', 19, 'male', 10) print(tea.name) print(tea.level)
單繼承下屬性查詢
class Foo: def f1(self): print('Foo.f1') def f2(self): # print('Foo.f2') self.f1() class Bar(Foo): def f1(self): print('Bar.f1') obj = Bar() # {} obj.f2() # 練習 class Foo: def __f1(self): # _Foo__f1() print('Foo.f1') def f2(self): # print('Foo.f2') self.__f1() # _Foo__f1() class Bar(Foo): def __f1(self): # # _Bar__f1() print('Bar.f1') obj = Bar() # {} obj.f2()
多繼承下的屬性查詢
# 新式類:按照廣度優先查詢 # 經典類:按照深度優先查詢 class A(object): def test(self): print('from A') class B(A): # def test(self): # print('from B') pass class C(A): # def test(self): # print('from C') pass class D(B): # def test(self): # print('from D') pass class E(C): # def test(self): # print('from E') pass class F(D, E): # def test(self): # print('from F') pass f1 = F() f1.test()
super()和mro列表
class People():
school = 'SH'
def __init__(self, name, age, gender):
self.name = name
self.age = age
self.gender = gender
class Teacher(People):
def __init__(self, name, age, gender, level):
self.level = level
super().__init__(name, age, gender) # super的使用
# mro列表練習1
class A:
def test(self):
print('from A.test')
super().test()
class B:
def test(self):
print('from B')
class C(A, B):
pass
c = C()
c.test()
# mro列表練習2
class B:
def test(self):
print('B---->test')
def aaa(self):
print('B---->aaa')
class A:
def test(self):
print('A---->test')
super().aaa()
class C(A, B):
def aaa(self):
print('C----->aaa')
c = A()
# c.test() # 列印結果:
print(A.mro())
多型與多型性(瞭解)
1. 什麼是多型
水:液態水,固態水,氣態水
動物:人,豬,狗,貓 ...
# 抽象類: 抽象類只能被繼承,不能被例項化
class Animal(metaclass=abc.ABCMeta):
@abc.abstractmethod # 該方法已經是抽象方法了
def speak(self): pass
@abc.abstractmethod
def login(self):pass
class People(Animal):
def speak(self):
# print('嗷嗷嗷')
pass
def login(self):
pass
class Pig(Animal):
def speak(self):
print('哼哼哼')
class Dog(Animal):
def speak(self):
print('汪汪汪')
obj = People()
obj.speak()
# 多型練習
class Pig():
def speak(self):
print('哼哼哼')
class Dog():
def speak(self):
print('汪汪汪')
class Txt():
def speak(self):
print('Txt')
obj = People()
obj1 = Pig()
obj2 = Dog()
obj3 = Txt()
# 多型帶來的特性:在不用考慮物件資料型別的情況下,直接呼叫對應的函式
def animal(animal):
return animal.speak()
animal(obj)
animal(obj1)
animal(obj2)
animal(obj3)
# 父類限制子類的行為
class Animal():
def speak(self):
raise Exception("必須實現speak方法")