Polymorphism Python

I am learning python and have question . After running this code ,the result displayed is

"Name is Bob and salary is50000 and work is main.PizzaRobot object at 0x00000000028EECC0>>"

I want "work" to be displayed for each object in str rather than calling obj.work() for each object .

In this problem output should be "Name is Bob and salary is50000 and work is Bob makes pizza"

Thanks

class Employee():
    def __init__(self,name,salary = 0):
        self.name = name
        self.salary = salary
    def giveraise(self,percent):
        self.salary = self.salary + self.salary * percent
    def __str__(self):
        return "Name is {0} and salary is{1} and work is {2}".format(self.name,self.salary,self.work)
    def work(self):
        print(self.name ,"does stuff")

class chef(Employee):
     def __init__(self,name):
         Employee.__init__(self,name,50000)
     def work(self):
         print(self.name ,"makes food")

class PizzaRobot(chef):
     def __init__(self,name):
         chef.__init__(self,name)
     def work(self):
         print(self.name ,"makes pizza")

if __name__ == "__main__":
    bob = PizzaRobot("Bob")
    print(bob)