Question

我到处研究过，虽然我发现了相同的概念，但我似乎无法找到错误的答案。

我之前没有发帖，因为我的帐号信息在堆栈上被遗忘了，但我对这个初学者的错误感到非常沮丧。

class Person(object):

    def __init__(self, name, phone):
        self.name = name
        self.phone = phone

class Employee(Person):

    total_salary = 0

    @staticmethod
    def total_salary(self, salary):
        return total_salary


    def __init__(self, name, phone, salary):
        self.name = name
        self.phone = phone
        self.salary = salary




class Student(Person):

    def __init__(self, name, phone, gpa):
        self.gpa = gpa
        self.name = name
        self.phone = phone

    def __str__(self):
        reply = ""
        reply = "Person " + self.name + " has phone " + self.phone + "\n" + " and is a Student with gpa " + str(self.gpa)
        return reply

class Professor(Employee):
    def __init__(self, name, phone, salary, clas_teach):
        self.clas_teach = clas_teach
        self.name = name
        self.phone = phone
        self.salary = salary

    def __str__(self):
        reply = ""
        reply = "Person " + self.name + " has phone " + self.phone + "\n" + " and is an Employee with salary " + str(self.salary) + "\n"
        reply += " and is a Professor assigned to class " + self.clas_teach
        return reply

class Staff(Employee):
    def __init__(self, name, phone, salary, position):
        self.position = position
        self.name = name
        self.phone = phone
        self.salary = salary
    def __str__(self):
        reply = ""
        reply = "Person " + self.name + " has phone " + self.phone + "\n" + " and is an Employee with salary " + str(self.salary) + "\n"
        reply += " and is Staff with title " + self.position
        return reply
# Create a list of people
People = [ Student("Sandy", "326-8324", 3.65), Student("Jordan", "632-7434", 3.1), \
           Professor("Leslie", "985-2363", 50000.00, "Info 501"),  \
           Staff("Alex", "743-4638", 25000.00, "Editor") ]

# display information about our people
print "These are the people in the university:"
for person in People:
   print person

# display the total salaries of all our employees and average GPA
#  of all of our students
print
print "Our total university payroll budget is: " + str(Employee.total_salary)
print "Our average student GPA is: " + str(Student.mean_gpa())

Answer 1

您的主要误解是课程如何运作。在您的代码中，您正在调用类而不是类的实例：

print "Our total university payroll budget is: " + str(Employee.total_salary)
print "Our average student GPA is: " + str(Student.mean_gpa())

这里的关键是：

Employee.total_salary

相反，你应该做这样的事情：

leslie = Professor("Leslie", "985-2363", 50000.00, "Info 501")
print "Leslie's Salary: " + str(leslie.salary)

对于这种特定情况，您需要总工资单，即所有员工工资的总和。你需要在某个地方收集员工。

def University():
    def __init__(self):
        self.employees[]

    def add_employee(self, employee):
        self.employees.append(employee)

    def get_total_payroll(self):
        total = 0
        for employee in self.employees:
            total += employee.salary
        return total

然后使用该类的实例：

university = University()
university.add_employee(Professor("Leslie", "985-2363", 50000.00, "Info 501"))
university.add_employee(Staff("Alex", "743-4638", 25000.00, "Editor"))

print "Total payroll: " + str(university.get_total_payroll())

显然，您需要做出更多调整，例如在员工和学生之间进行排序等。但希望这足以让您入门。

Answer 2

您的整体设计存在问题已在其他答案中介绍，因此我将尝试解释您当前代码无效的原因：

您已创建名为total_salary的类属性，然后使用相同名称的方法对其进行遮蔽。
当您需要使用类方法时，您正在使用静态方法。
您需要调用total_salary作为方法才能返回其值。

这些问题可以这样解决：

class Employee(Person):
    _total_salary = 0

    @classmethod
    def total_salary(cls):
        return cls._total_salary
...

print "Our total university payroll budget is: " + str(Employee.total_salary())

但请注意，代码仍然会引发AttributeError，因为您正在尝试调用尚未定义的Student.mean_gpa。

Answer 3

您的类Employee具有属性AND具有相同名称的方法。调用Employee.total_salary将返回该函数，因为在MRO中它正在替换属性。

变化：

class Employee(Person):
    total_salary = 0

到

class Employee(Person):
    total_salary_value = 0

staticmethod total_salary中的Employee正在返回一个不存在的变量（因为它只在方法范围内查找），您应该返回Employee.total_salary_value。像这样：

@staticmethod
def total_salary():
    return Employee.total_salary_value

在__init__的{{1}}中，您没有实例化您继承的Employee（Person中的相同内容（继承Student），{ {1}}和Person（都继承Professor）

使用：

Staff

或

Employee

仍然在init中，您没有将薪水添加到Person.__init__(self,name,phone)

添加：

super(Employee, self).__init__(name, phone)

此外，您无需在total_salary_value中使用Employee.total_salary_value += self.salary和self.name，因为self.phone已具有此属性。（Student和Person）

中的变量和其他变量相同

最后，Professor没有名为Staff的方法。你必须实现它。

以下是代码：

Student

编辑：

正如@ekhumoro所说，最好使用@classmethod来返回值。

另一方面，使用.format（）

可以使您的mean_gpa更加清晰

未绑定错误Python类

3 个答案: