Why did I get a "None" value of the parameter in subclass?

Question

I'm new to python (and coding) and I've been trying to expand my knowledge by youtube tutorials. When watching a chapter about classes I have created a class and a sub class and I don't know why I get the results as they are. Can you help me?

This is my code:

class Person:
    def __init__(self, name, age, height):
        self.name = name
        self.age = age
        self.height = height

    def print_info(self):
        print(self.name + ", age " + self.age + ", height " + self.height + "cm.")


class Employee(Person):
    def  __init__(self, name, age, height, id_number):
        Person.__init__(self, name, age, height)
        self.id_number = id_number

    def print_employee_info(self):
        print(str(Person.print_info(self)) + self.id_number)

john = Employee("John", "20", "182", "2230")
john.print_employee_info()

I expected it to print:

"John, age 20, height 182cm.2230"

What I got is:

"John, age 20, height 182cm 
None2230"

So I believe it that it prints in new line "None2230" because I call the method Person.print_info(self) ?

What I don't know is why there is "None" added to id_number and how can I fix this?

If anything else bothers you, just write it down I'd like to learn.

Thanks a lot for the answers.

Much appreciated.

Answer 1

You want your print_info method to return a string rather than printing it. Try changing it to this:

    def print_info(self):
        return self.name + ", age " + self.age + ", height " + self.height + "cm."

Then your print_employee_info can just be

    def print_employee_info(self):
        print(self.print_info() + self.id_number)