Python面向对象编程基础实例分析

class Person(object):  # 定义一个Person类
  pass
p = Person()  # 初始化一个Person对象
p.name="xiaoming"  # 对象属性赋值

class Person(object):
  count = 0  # 类属性
  @classmethod:
  def get_count(cls):  # 类方法
    return cls.count
  def __init__(self,name,gender,birth,**kw):
    Person.count+=1  # 访问类属性
    self.name = name
    self.__gender = gender
    self.birth = birth
    for k, v in kw.iteritems():  # 遍历之后的键值对，设置属性
      setattr(self, k, v)
  def get_name(self):  # 定义实例方法
    return self.__name
xiaoming = Person('Xiao Ming', 'Male', '1990-1-1', job='Student')
xiaoming.count==9  # 为对象创建属性，不会修改Person.count
print(xiaoming.job)  # 显示Student
print(xiaoming.__gender)  # 无法访问，抛出异常AttributeError
print(xiaoming.get_name())  # 通过实例方法访问内部变量

class Person(object):
  def __init__(self, name, gender):
    self.name = name
    self.gender = gender
class Teacher(Person):  # 继承父类Person
  def __init__(self, name, gender, course):
    super(Teacher,self).__init__(name,gender)  # 调用父类的初始化函数
    self.course= course  # 完成子类变量的初始化
t = Teacher('Alice', 'Female', 'English')
print(isinstance(t,Person))  # 结果为True，子类也是父类的类型
print(dir(t))  # 显示对象的所有属性

import json
class Students(object):
  def read(self):
    return r'["Tim", "Bob", "Alice"]'
s = Students()
print json.load(s)

class A(object):
  def __init__(self, a):
    self.a = a
class B(object):
  def __init__(self, b):
    self.b = b
class C(A, B):
  def __init__(self, a, b, c):
    A.__init__(self, a)
    B.__init__(self, b)
    self.c = c
c = C(1, 2, 3)
print(c.a)   # 输出1

class Person(object):
  def __init__(self, name, gender):
    self.name = name
    self.gender = gender
  def __str__(self):  # 重新定义类特殊方法
    return "My name is " + self.name
p = Person('Bob', 'male')
print(p)  # 输出结果为：My name is Bob

class Student(object):
  def __init__(self, name, score):
    self.name = name
    self.score = score
  def __cmp__(self, s):  # 重写__cmp__方法
    if self.score>s.score:
      return -1  # self在s之前
    elif self.score<s.score:
      return 1
    else:
      return 0
L = [Student('Tim', 99), Student('Bob', 88), Student('Alice', 99)]
Ls = sorted(L)  # 使用sorted对Student类进行排序

def gcd(a, b):  # 求最大公约数
  if b == 0:
    return a
  return gcd(b, a % b)
class Rational(object):
  def __init__(self, p, q):
    self.p = p
    self.q = q
  def __add__(self, r):  # 重写加法运算
    return Rational(self.p * r.q + self.q * r.p, self.q * r.q)
  def __str__(self):
    g = gcd(self.p, self.q)  # 将分数约分后输出
    return '%s/%s' % (self.p / g, self.q / g)
  def __float__(self):  # 将分数转化为float小数返回
    return float(self.p)/float(self.q)
r1 = Rational(1, 2)
r2 = Rational(1, 4)
print(r1 + r2)  # 两个类相加
print(float(r1))  # 输出小数形式

class Student(object):
  __slots__ = ('name','__score')  # 本类只允许使用name、score两个属性
  def __init__(self, name, score):
    self.name = name
    self.__score = score
  @property        # 定义属性返回方法
  def score(self):
    return self.__score
  @score.setter      # 定义属性设置方法
  def score(self, score):
    if score < 0 or score > 100:
      raise ValueError('invalid score')
    self.__score = score
  def __call__(self, friend):
    print('My friend is %s...' % friend)
s = Student('Bob', 59)
s.score = 60  # 调用属性设置方法
print(s.score)  # 调用属性返回方法
s.grade='A'  # 抛出异常，无法添加其他属性
s('Alice')  # 输出My friend is Alice...

# 文件a.py中
import b
print(b.func1())
# 直接引入函数
from b import func1
print(func1())
# 使用别名
from b import func1 as f1
print(f1())

# p1/a.py文件内
import p2.b
print (p2.b.func2())