详解详细介绍l了Python类的继承

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(&＃39;Alice&＃39;, &＃39;Female&＃39;, &＃39;English&＃39;)
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(&＃39;Alice&＃39;, &＃39;Female&＃39;, &＃39;English&＃39;)

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 &＃39;I am a Person, my name is %s&＃39; % self.name

class Student(Person):
    def init(self, name, gender, score):
        super(Student, self).init(name, gender)
        self.score = score
    def whoAmI(self):
        return &＃39;I am a Student, my name is %s&＃39; % self.name

class Teacher(Person):
    def init(self, name, gender, course):
        super(Teacher, self).init(name, gender)
        self.course = course
    def whoAmI(self):
        return &＃39;I am a Teacher, my name is %s&＃39; % self.name
        
        
import json

class Students(object):
    def read(self):
        return r&＃39;["Tim", "Bob", "Alice"]&＃39;

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 &＃39;init A...&＃39;
        self.a = a

class B(A):
    def init(self, a):
        super(B, self).init(a)
        print &＃39;init B...&＃39;

class C(A):
    def init(self, a):
        super(C, self).init(a)
        print &＃39;init C...&＃39;

class D(B, C):
    def init(self, a):
        super(D, self).init(a)
        print &＃39;init D...&＃39;
        
        
class Person(object):
    pass

class Student(Person):
    pass

class Teacher(Person):
    pass

class SkillMixin(object):
    pass

class BasketballMixin(SkillMixin):
    def skill(self):
        return &＃39;basketball&＃39;

class FootballMixin(SkillMixin):
    def skill(self):
        return &＃39;football&＃39;

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 &＃39;I am a Student, my name is %s&＃39; % self.name

print type(123) # 

s = Student(&＃39;Bob&＃39;, &＃39;Male&＃39;, 88)
print s  # 

print dir(123) # [&＃39;abs&＃39;, &＃39;add&＃39;, &＃39;and&＃39;, &＃39;class&＃39;, &＃39;cmp&＃39;, &＃39;coerce&＃39;, &＃39;delattr&＃39;, &＃39;p&＃39;, &＃39;pmod&＃39;, &＃39;doc&＃39;, &＃39;float&＃39;, &＃39;floorp&＃39;, &＃39;format&＃39;, &＃39;getattribute&＃39;, &＃39;getnewargs&＃39;, &＃39;hash&＃39;, &＃39;hex&＃39;, &＃39;index&＃39;, &＃39;init&＃39;, &＃39;int&＃39;, &＃39;invert&＃39;, &＃39;long&＃39;, &＃39;lshift&＃39;, &＃39;mod&＃39;, &＃39;mul&＃39;, &＃39;neg&＃39;, &＃39;new&＃39;, &＃39;nonzero&＃39;, &＃39;oct&＃39;, &＃39;or&＃39;, &＃39;pos&＃39;, &＃39;pow&＃39;, &＃39;radd&＃39;, &＃39;rand&＃39;, &＃39;rp&＃39;, &＃39;rpmod&＃39;, &＃39;reduce&＃39;, &＃39;reduce_ex&＃39;, &＃39;repr&＃39;, &＃39;rfloorp&＃39;, &＃39;rlshift&＃39;, &＃39;rmod&＃39;, &＃39;rmul&＃39;, &＃39;ror&＃39;, &＃39;rpow&＃39;, &＃39;rrshift&＃39;, &＃39;rshift&＃39;, &＃39;rsub&＃39;, &＃39;rtruep&＃39;, &＃39;rxor&＃39;, &＃39;setattr&＃39;, &＃39;sizeof&＃39;, &＃39;str&＃39;, &＃39;sub&＃39;, &＃39;subclasshook&＃39;, &＃39;truep&＃39;, &＃39;trunc&＃39;, &＃39;xor&＃39;, &＃39;bit_length&＃39;, &＃39;conjugate&＃39;, &＃39;denominator&＃39;, &＃39;imag&＃39;, &＃39;numerator&＃39;, &＃39;real&＃39;]

print dir(s) # [&＃39;class&＃39;, &＃39;delattr&＃39;, &＃39;dict&＃39;, &＃39;doc&＃39;, &＃39;format&＃39;, &＃39;getattribute&＃39;, &＃39;hash&＃39;, &＃39;init&＃39;, &＃39;module&＃39;, &＃39;new&＃39;, &＃39;reduce&＃39;, &＃39;reduce_ex&＃39;, &＃39;repr&＃39;, &＃39;setattr&＃39;, &＃39;sizeof&＃39;, &＃39;str&＃39;, &＃39;subclasshook&＃39;, &＃39;weakref&＃39;, &＃39;gender&＃39;, &＃39;name&＃39;, &＃39;score&＃39;, &＃39;whoAmI&＃39;]

print getattr(s, &＃39;name&＃39;) # Bob
setattr(s, &＃39;name&＃39;, &＃39;Adam&＃39;) 
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(&＃39;Bob&＃39;, &＃39;Male&＃39;, age=18, course=&＃39;Python&＃39;)
print p.age # 18
print p.course #Python

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