#!/usr/local/bin/python
# Fig 9.9: fig09_09.py
# Creating a class hierarchy with an abstract base class.
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class Employee:
?? """Abstract base class Employee"""
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?? def __init__(self, first, last):
????? """Employee constructor, takes first name and last name.
????? NOTE: Cannot create object of class Employee."""
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????? if self.__class__ == Employee:
???????? raise NotImplementedError, \
??????????? "Cannot create object of class Employee"
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????? self.firstName = first
????? self.lastName = last
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?? def __str__(self):
????? """String representation of Employee"""
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????? return "%s %s" % (self.firstName, self.lastName)
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?? def _checkPositive(self, value):
????? """Utility method to ensure a value is positive"""
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????? if value < 0:
???????? raise ValueError, \
??????????? "Attribute value (%s) must be positive" % value
????? else:
???????? return value
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?? def earnings(self):
????? """Abstract method; derived classes must override"""
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????? raise NotImplementedError, "Cannot call abstract method"
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class Boss(Employee):
?? """Boss class, inherits from Employee"""
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?? def __init__(self, first, last, salary):
????? """Boss constructor, takes first and last names and salary"""
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????? Employee.__init__(self, first, last)
????? self.weeklySalary = self._checkPositive(float(salary))
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?? def earnings(self):
????? """Compute the Boss's pay"""
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????? return self.weeklySalary
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?? def __str__(self):
????? """String representation of Boss"""
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????? return "%17s: %s" % ("Boss", Employee.__str__(self))
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class CommissionWorker(Employee):
?? """CommissionWorker class, inherits from Employee"""
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?? def __init__(self, first, last, salary, commission, quantity):
????? """CommissionWorker constructor, takes first and last names,
????? salary, commission and quantity"""
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????? Employee.__init__(self, first, last)
????? self.salary = self._checkPositive(float(salary))
????? self.commission = self._checkPositive(float(commission))
????? self.quantity = self._checkPositive(quantity)
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?? def earnings(self):
????? """Compute the CommissionWorker's pay"""
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????? return self.salary + self.commission * self.quantity
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?? def __str__(self):
????? """String representation of CommissionWorker"""
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????? return "%17s: %s" % ("Commission Worker",
???????? Employee.__str__(self))
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class PieceWorker(Employee):
?? """PieceWorker class, inherits from Employee"""
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?? def __init__(self, first, last, wage, quantity):
????? """PieceWorker constructor, takes first and last names, wage
????? per piece and quantity"""
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????? Employee.__init__(self, first, last)
????? self.wagePerPiece = self._checkPositive(float(wage))
????? self.quantity = self._checkPositive(quantity)
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?? def earnings(self):
????? """Compute PieceWorker's pay"""
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????? return self.quantity * self.wagePerPiece
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?? def __str__(self):
????? """String representation of PieceWorker"""
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????? return "%17s: %s" % ("Piece Worker",
???????? Employee.__str__(self))
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class HourlyWorker(Employee):
?? """HourlyWorker class, inherits from Employee"""
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?? def __init__(self, first, last, wage, hours):
????? """HourlyWorker constructor, takes first and last names,
????? wage per hour and hours worked"""
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????? Employee.__init__(self, first, last)
????? self.wage = self._checkPositive(float(wage))
????? self.hours = self._checkPositive(float(hours))
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?? def earnings(self):
????? """Compute HourlyWorker's pay"""
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????? if self.hours <= 40:
???????? return self.wage * self.hours
????? else:
???????? return 40 * self.wage + (self.hours - 40) * \
?????????? self.wage * 1.5
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?? def __str__(self):
????? """String representation of HourlyWorker"""
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????? return "%17s: %s" % ("Hourly Worker",
???????? Employee.__str__(self))
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# main program
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# 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) ]
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# print Employee and compute earnings
for employee in employees:
?? print "%s earned $%.2f" % (employee, employee.earnings())