linux下python学习笔记(十六）

#!/usr/bin/python

# Filename: objvar.py

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()



记住，你只能使用self变量来参考同一个对象的变量和方法。这被称为 属性参考 。

只有一个例外：如果你使用的数据成员名称以 双下划线前缀 比如__privatevar，Python的名称管理体系会有效地把它作为私有变量。

这样就有一个惯例，如果某个变量只想在类或对象中使用，就应该以单下划线前缀。而其他的名称都将作为公共的，可以被其他类/对象使用。记住这只是一个惯例，并不是Python所要求的（与双下划线前缀不同）。

继承

面向对象的编程带来的主要好处之一是代码的重用，实现这种重用的方法之一是通过 继承 机制。

#!/usr/bin/python

# Filename: inherit.py

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



Python不会自动调用基本类的constructor，你得亲自专门调用它。