【python自学】（七）-----面向对象编程

self

self类似于C或者C++中的this

类

创建类

__init__

构造函数，类似于constructor；__del__类似于析构函数。

类与对象的方法

类与对象的变量

类与对象的数据部分：类与对象那个的名称空间绑定的普通变量，即这些名称只在这些类与对象的前提下有效。有两种类型的域--类的变量与对象的变量，它们根据是类还是变量拥有这个变量而进行区分。类的变量由这个类的所有对象共享使用，对象的变量由某个对象肚子拥有。python中所有的类成员（数据部分以及功能部分）都是公共的，如果使用的数据成员名称以双下划线前缀例如__privatevar，python的名称管理体系将把它作为私有变量。所以如果某个变量只想在类或者对象中使用，就可以使用双下划线的前缀。

class Person:
    '''Represents a person.'''
    population = 0

    def __init__(self, name):
        '''Initializes the person's data.'''
        self.name = name
        print '(Initializing %s)' % self.name

        # When this person is created, he/she
        # adds to the population
        Person.population += 1

    def __del__(self):
        '''I am dying.'''
        print '%s says bye.' % self.name

        Person.population -= 1

        if Person.population == 0:
            print 'I am the last one.'
        else:
            print 'There are still %d people left.' % Person.population

    def sayHi(self):
        '''Greeting by the person.

        Really, that's all it does.'''
        print 'Hi, my name is %s.' % self.name

    def howMany(self):
        '''Prints the current population.'''
        if Person.population == 1:
            print 'I am the only person here.'
        else:
            print 'We have %d persons here.' % Person.population

swaroop = Person('Swaroop')
swaroop.sayHi()
swaroop.howMany()

kalam = Person('Abdul Kalam')
kalam.sayHi()
kalam.howMany()

swaroop.sayHi()
swaroop.howMany()

Hi, my name is Swaroop.
I am the only person here.
(Initializing Abdul Kalam)
Hi, my name is Abdul Kalam.
We have 2 persons here.
Hi, my name is Swaroop.
We have 2 persons here.
Abdul Kalam says bye.
There are still 1 people left.
Swaroop says bye.
I am the last one.

继承

class SchoolMember:
    '''Represents any school member.'''
    def __init__(self, name, age):
        self.name = name
        self.age = age
        print '(Initialized SchoolMember: %s)' % self.name

    def tell(self):
        '''Tell my details.'''
        print 'Name:"%s" Age:"%s"' % (self.name, self.age),

class Teacher(SchoolMember):
    '''Represents a teacher.'''
    def __init__(self, name, age, salary):
        SchoolMember.__init__(self, name, age)
        self.salary = salary
        print '(Initialized Teacher: %s)' % self.name

    def tell(self):
        SchoolMember.tell(self)
        print 'Salary: "%d"' % self.salary

class Student(SchoolMember):
    '''Represents a student.'''
    def __init__(self, name, age, marks):
        SchoolMember.__init__(self, name, age)
        self.marks = marks
        print '(Initialized Student: %s)' % self.name

    def tell(self):
        SchoolMember.tell(self)
        print 'Marks: "%d"' % self.marks

t = Teacher('Mrs. Shrividya', 40, 30000)
s = Student('Swaroop', 22, 75)

print # prints a blank line

members = [t, s]
for member in members:
    member.tell() # works for both Teachers and Students

(Initialized SchoolMember: Mrs. Shrividya)
(Initialized Teacher: Mrs. Shrividya)
(Initialized SchoolMember: Swaroop)
(Initialized Student: Swaroop)

Name:"Mrs. Shrividya" Age:"40" Salary: "30000"
Name:"Swaroop" Age:"22" Marks: "75"

使用继承的方法是class 子类名称（父类名称）；同时，基类的构造函数需要使用self调用，这样才可以在子类中初始化基类部分，python不会调用基类的构造函数，需要亲自调用（调用时需要在方法前添加类名称前缀，然后将self变量以及其他参数传递给它）。

【python自学】（七）-----面向对象编程

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