Work with Several Independent Objects

In the previous lesson, self referred to first during one method call and second during another. That change is possible because both names lead to separate objects created from the same class.

A program can create as many Question instances as it needs:

first = Question("Two plus two?", "4")
second = Question("Three plus three?", "6")

Both instances follow the same Question definition, but each one keeps its own state.

Changing an attribute on first does not change second:

first.prompt = "What is two plus two?"
print(first.prompt)
print(second.prompt)

That independence is one reason objects are useful for modeling several records of the same kind.

Objects fit inside collections

An object is a Python value, so a list can hold objects just as it holds strings or dictionaries:

questions = [first, second]

for question in questions:
    print(question.prompt)

The loop variable refers to a different Question instance on each pass.

Names are not objects

The variable name is only one way to reach an object:

current = first

Now current and first refer to the same object. This does not create a copy.

current.prompt = "Updated prompt"
print(first.prompt)

The output is Updated prompt because both names lead to one instance.

The next lesson will give another object a collection of questions and let the objects work together.