python demo

1.类属性

#!/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()

输出

$ python objvar.py
(Initializing Swaroop)
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.

还有一个特殊的方法del，它在对象消逝的时候被调用

2.继承

#!/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

结果

$ python inherit.py
(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"