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：

复制代码 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):
      \”\”\”CommissionWorker constructor, takes first and last names,
      salary, commission and quantity\”\”\”
 
      Employee.__init__(self, first, last)
      self.salary = self._checkPositive(float(salary))
      self.commission = self._checkPositive(float(commission))
      self.quantity = self._checkPositive(quantity)
 
   def earnings(self):
      \”\”\”Compute the CommissionWorker\’s pay\”\”\”
 
      return self.salary + self.commission * self.quantity
 
   def __str__(self):
      \”\”\”String representation of CommissionWorker\”\”\”
 
      return \”%17s: %s\” % (\”Commission Worker\”,
         Employee.__str__(self))
 
class PieceWorker(Employee):
   \”\”\”PieceWorker class, inherits from Employee\”\”\”
 
   def __init__(self, first, last, wage, quantity):
      \”\”\”PieceWorker constructor, takes first and last names, wage
      per piece and quantity\”\”\”
 
      Employee.__init__(self, first, last)
      self.wagePerPiece = self._checkPositive(float(wage))
      self.quantity = self._checkPositive(quantity)
 
   def earnings(self):
      \”\”\”Compute PieceWorker\’s pay\”\”\”
 
      return self.quantity * self.wagePerPiece
 
   def __str__(self):
      \”\”\”String representation of PieceWorker\”\”\”
 
      return \”%17s: %s\” % (\”Piece Worker\”,
         Employee.__str__(self))
 
class HourlyWorker(Employee):
   \”\”\”HourlyWorker class, inherits from Employee\”\”\”
 
   def __init__(self, first, last, wage, hours):
      \”\”\”HourlyWorker constructor, takes first and last names,
      wage per hour and hours worked\”\”\”
 
      Employee.__init__(self, first, last)
      self.wage = self._checkPositive(float(wage))
      self.hours = self._checkPositive(float(hours))
 
   def earnings(self):
      \”\”\”Compute HourlyWorker\’s pay\”\”\”
 
      if self.hours <= 40:
         return self.wage * self.hours
      else:
         return 40 * self.wage + (self.hours – 40) * \\
           self.wage * 1.5
 
   def __str__(self):
      \”\”\”String representation of HourlyWorker\”\”\”
 
      return \”%17s: %s\” % (\”Hourly Worker\”,
         Employee.__str__(self))
 
# main program
 
# create list of Employees
employees = [ Boss(\”John\”, \”Smith\”, 800.00),
              CommissionWorker(\”Sue\”, \”Jones\”, 200.0, 3.0, 150),
              PieceWorker(\”Bob\”, \”Lewis\”, 2.5, 200),
              HourlyWorker(\”Karen\”, \”Price\”, 13.75, 40) ]
 
# print Employee and compute earnings
for employee in employees:
   print \”%s earned $%.2f\” % (employee, employee.earnings())

输出结果如下：

Boss: John Smith earned $800.00

Commission Worker: Sue Jones earned $650.00

Piece Worker: Bob Lewis earned $500.00

Hourly Worker: Karen Price earned $550.00

希望本文所述对大家的Python程序设计有所帮助。