贪狼棋子和松子,财经天下,支柱蓼
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：
#!/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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