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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。

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