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。