本文實(shí)例講述了python繼承和抽象類的實(shí)現(xiàn)方法。分享給大家供大家參考。
具體實(shí)現(xiàn)方法如下:
# 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())
輸出結(jié)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
希望本文所述對(duì)大家的Python程序設(shè)計(jì)有所幫助。
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