python类的继承(进阶5)
1. python中什么是继承
python中什么是继承:
新类不必从头编写 新类从现有的类继承，就自动拥有了现有类的所有功能 新类只需要编写现有类缺少的新功能继承的好处：
复用已有代码 自动拥有了现有类的所有功能 只需要编写缺少的新功能继承的特点：
子类和父类是is关系python继承的特点：
总是从某个类继承 不要忘记调用super(). init 2. python中继承一个类 class Person(object): def __init__(self, name, gender): self.name = name self.gender = gender class Teacher(Person): def __init__(self, name, gender, course): super(Teacher, self).__init__(name, gender) self.course = course t = Teacher('Alice', 'Female', 'English') print t.name print t.course 3. python中判断类型函数isinstance()可以判断一个变量的类型，既可以用在Python内置的数据类型如str、list、dict，也可以用在我们自定义的类，它们本质上都是数据类型。
class Person(object): def __init__(self, name, gender): self.name = name self.gender = gender class Student(Person): def __init__(self, name, gender, score): super(Student, self).__init__(name, gender) self.score = score class Teacher(Person): def __init__(self, name, gender, course): super(Teacher, self).__init__(name, gender) self.course = course t = Teacher('Alice', 'Female', 'English') print isinstance(t, Person) print isinstance(t, Student) print isinstance(t, Teacher) print isinstance(t, object) 4. python中多态 class Person(object): def __init__(self, name, gender): self.name = name self.gender = gender def whoAmI(self): return 'I am a Person, my name is %s' % self.name class Student(Person): def __init__(self, name, gender, score): super(Student, self).__init__(name, gender) self.score = score def whoAmI(self): return 'I am a Student, my name is %s' % self.name class Teacher(Person): def __init__(self, name, gender, course): super(Teacher, self).__init__(name, gender) self.course = course def whoAmI(self): return 'I am a Teacher, my name is %s' % self.name import json class Students(object): def read(self): return r'["Tim", "Bob", "Alice"]' s = Students() print json.load(s) 5. python中多重继承除了从一个父类继承外，Python允许从多个父类继承，称为多重继承。Java不能多继承
class A(object): def __init__(self, a): print 'init A...' self.a = a class B(A): def __init__(self, a): super(B, self).__init__(a) print 'init B...' class C(A): def __init__(self, a): super(C, self).__init__(a) print 'init C...' class D(B, C): def __init__(self, a): super(D, self).__init__(a) print 'init D...' class Person(object): pass class Student(Person): pass class Teacher(Person): pass class SkillMixin(object): pass class BasketballMixin(SkillMixin): def skill(self): return 'basketball' class FootballMixin(SkillMixin): def skill(self): return 'football' class BStudent(BasketballMixin): pass class FTeacher(FootballMixin): pass s = BStudent() print s.skill() t = FTeacher() print t.skill() 6. python中获取对象信息除了用 isinstance() 判断它是否是某种类型的实例外，还有没有别的方法获取到更多的信息呢？
首先可以用 type() 函数获取变量的类型，它返回一个 Type 对象
dir() 函数获取变量的所有属性
dir()返回的属性是字符串列表，如果已知一个属性名称，要获取或者设置对象的属性，就需要用 getattr() 和 setattr( )函数了
class Person(object): def __init__(self, name, gender): self.name = name self.gender = gender class Student(Person): def __init__(self, name, gender, score): super(Student, self).__init__(name, gender) self.score = score def whoAmI(self): return 'I am a Student, my name is %s' % self.name print type(123) # <type 'int'> s = Student('Bob', 'Male', 88) print s # <class '__main__.Student'> print dir(123) # ['__abs__', '__add__', '__and__', '__class__', '__cmp__', '__coerce__', '__delattr__', '__div__', '__divmod__', '__doc__', '__float__', '__floordiv__', '__format__', '__getattribute__', '__getnewargs__', '__hash__', '__hex__', '__index__', '__init__', '__int__', '__invert__', '__long__', '__lshift__', '__mod__', '__mul__', '__neg__', '__new__', '__nonzero__', '__oct__', '__or__', '__pos__', '__pow__', '__radd__', '__rand__', '__rdiv__', '__rdivmod__', '__reduce__', '__reduce_ex__', '__repr__', '__rfloordiv__', '__rlshift__', '__rmod__', '__rmul__', '__ror__', '__rpow__', '__rrshift__', '__rshift__', '__rsub__', '__rtruediv__', '__rxor__', '__setattr__', '__sizeof__', '__str__', '__sub__', '__subclasshook__', '__truediv__', '__trunc__', '__xor__', 'bit_length', 'conjugate', 'denominator', 'imag', 'numerator', 'real'] print dir(s) # ['__class__', '__delattr__', '__dict__', '__doc__', '__format__', '__getattribute__', '__hash__', '__init__', '__module__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', '__weakref__', 'gender', 'name', 'score', 'whoAmI'] print getattr(s, 'name') # Bob setattr(s, 'name', 'Adam') print s.name # Adam class Person(object): def __init__(self, name, gender, **kw): self.name = name self.gender = gender for k, v in kw.iteritems(): setattr(self, k, v) p = Person('Bob', 'Male', age=18, course='Python') print p.age # 18 print p.course #Python