1.编写一个Date类，有checkMonth和checkDay函数以检查月份和日期的合法性，有判断是否为闰年的函数，设计定义set类函数，用以设定年，月份和日期，设计定义多个get函数用以获取年、月和日。 2. 创建一个抽象类employee类，该类中有姓名（sting 类型），ID（sting 类型）和出生日期(Date类型)。定义构造函数初始化每个成员；定义changeName()函数用来修改姓名，定义Display()函数用来显示每个员工的基本信息。纯虚函数为发放工资函数。 3.创建由Employee类派生出的其它四个员工类Salaried Employee,Commission Employee，Hourly Employee,以及由Commission Employee派生出的BasePlus Commission Employee。编写他们的新增成员、构造函数等，他们都有一个计算工资的函数。

1. Date类的代码实现如下：

class Date:
    def __init__(self):
        self.year = None
        self.month = None
        self.day = None
    
    def set_date(self, year, month, day):
        if self.check_month(month) and self.check_day(year, month, day):
            self.year = year
            self.month = month
            self.day = day
        else:
            print("Invalid date!")
            
    def check_month(self, month):
        return month in range(1, 13)
    
    def check_day(self, year, month, day):
        if month == 2:
            if self.is_leap_year(year):
                return day in range(1, 30)
            else:
                return day in range(1, 29)
        elif month in [4, 6, 9, 11]:
            return day in range(1, 31)
        else:
            return day in range(1, 32)
        
    def is_leap_year(self, year):
        return (year % 4 == 0 and year % 100 != 0) or year % 400 == 0
    
    def get_year(self):
        return self.year
    
    def get_month(self):
        return self.month
    
    def get_day(self):
        return self.day

2. 抽象类Employee类的代码实现如下：

from abc import ABCMeta, abstractmethod

class Employee(metaclass=ABCMeta):
    def __init__(self, name, id, birth_date):
        self.name = name
        self.id = id
        self.birth_date = birth_date
        
    def change_name(self, new_name):
        self.name = new_name
        
    def display(self):
        print(f"Name: {self.name}")
        print(f"ID: {self.id}")
        print(f"Birth date: {self.birth_date.get_year()}/{self.birth_date.get_month()}/{self.birth_date.get_day()}\n")

    @abstractmethod
    def pay_salary(self):
        pass

3. 四个员工类和计算工资函数的代码实现如下：

class SalariedEmployee(Employee):
    def __init__(self, name, id, birth_date, monthly_salary):
        super().__init__(name, id, birth_date)
        self.monthly_salary = monthly_salary
        
    def pay_salary(self):
        return self.monthly_salary
    
class CommissionEmployee(Employee):
    def __init__(self, name, id, birth_date, sales, commission_rate):
        super().__init__(name, id, birth_date)
        self.sales = sales
        self.commission_rate = commission_rate
        
    def pay_salary(self):
        return self.sales * self.commission_rate
    
class HourlyEmployee(Employee):
    def __init__(self, name, id, birth_date, hourly_wage, hours_worked):
        super().__init__(name, id, birth_date)
        self.hourly_wage = hourly_wage
        self.hours_worked = hours_worked
        
    def pay_salary(self):
        if self.hours_worked <= 40:
            return self.hourly_wage * self.hours_worked
        else:
            return self.hourly_wage * 40 + self.hourly_wage * 1.5 * (self.hours_worked - 40)
        
class BasePlusCommissionEmployee(CommissionEmployee):
    def __init__(self, name, id, birth_date, sales, commission_rate, base_salary):
        super().__init__(name, id, birth_date, sales, commission_rate)
        self.base_salary = base_salary
        
    def pay_salary(self):
        return super().pay_salary() + self.base_salary

这些类可以用来创建具体的员工对象，并调用其方法来进行操作，比如：

# 创建一个Date对象
d = Date()

# 设置日期
d.set_date(2021, 2, 29)

# 创建一个SalariedEmployee对象
se = SalariedEmployee("Tom", "001", d, 5000)

# 显示员工信息
se.display()

# 计算工资
salary = se.pay_salary()
print(f"Salary: {salary}")