python继承和抽象类的实现方法

本文实例讲述了python继承和抽象类的实现方法。分享给大家供大家参考。

具体实现方法如下：

代码如下:#!/usr/local/bin/python
# Fig 9.9: fig09_09.py
# Creating a class hierarchy with an abstract base class.
 
class Employee:
   """Abstract base class Employee"""
 
   def __init__(self, first, last):
      """Employee constructor, takes first name and last name.
      NOTE: Cannot create object of class Employee."""
 
      if self.__class__ == Employee:
         raise NotImplementedError, /
            "Cannot create object of class Employee"
 
      self.firstName = first
      self.lastName = last
 
   def __str__(self):
      """String representation of Employee"""
 
      return "%s %s" % (self.firstName, self.lastName)
 
   def _checkPositive(self, value):
      """Utility method to ensure a value is positive"""
 
      if value < 0:
         raise ValueError, /
            "Attribute value (%s) must be positive" % value
      else:
         return value
 
   def earnings(self):
      """Abstract method; derived classes must override"""
 
      raise NotImplementedError, "Cannot call abstract method"
 
class Boss(Employee):
   """Boss class, inherits from Employee"""
 
   def __init__(self, first, last, salary):
      """Boss constructor, takes first and last names and salary"""
 
      Employee.__init__(self, first, last)
      self.weeklySalary = self._checkPositive(float(salary))
 
   def earnings(self):
      """Compute the Boss's pay"""
 
      return self.weeklySalary
 
   def __str__(self):
      """String representation of Boss"""
 
      return "%17s: %s" % ("Boss", Employee.__str__(self))
 
class CommissionWorker(Employee):
   """CommissionWorker class, inherits from Employee"""
 
   def __init__(self, first, last, salary, commission, quantity):