Why wouldn't I use this as real code? [4:30]

I understand the confusion here. The "magic"/"dunder"/"double underscore" methods that Kenneth is demonstrating is Python's version of a very important OOP concept (method overloading). Essentially, this allows you to change the default behavior of your class in relation to various uses.

Take the following Person class:

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

employee = Person("Adam", 45)

print(employee.name)
print(employee.age)

print(len(employee))

This script would produce the following error:

TypeError: object of type 'Person' has no len()

this is because the Person class is not an iterable and the len behavior hasn't been defined.

So if we change our class to something like:

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

  def __len__(self):
      return 2

employee = Person("Adam", 45)

print(employee.name)
print(employee.age)

print(len(employee))

We would get the expected output:

Adam
45
2

This is because we specified to always return the integer 2 when using the len property. This is probably not useful and wouldn't likely be implmented if you were to use this Person class. What kenneth did was override many common double underscore methods to return

float(self.value)
or
int(self.value)

when the int or float methods were called. What if the person implementing the class provided the string "Hello" as the init value when instantiating the class? This can result in unhandled ValueErrors. In a real production application, it is best to only overload methods when you have a specific need or purpose and have properly handled any errors. Of course, Kenneth was just doing a demo so no harm, no foul.

The concept of method overloading is a very important concept of OOP and is would be well worth your time to look into it and spend time reading documentation or watching videos. It can be overwhelming and you may not get a full grasp at first. If you keep using OOP, you'll find that you will eventually need to use these methods and then it will help you understand how and why to use them.

I hope this helps.