Question

Make a class called Thing with no contents and print it. Then, create an object called example from this class and also print it. Are the printed values the same or different?

Short answer

The printed values are different; the class and the object instance have distinct outputs.

Step-by-step solution

Define the Class

Create a class named `Thing` in Python using the `class` keyword with nothing inside it. This class is essentially empty, serving as a placeholder without any attributes or methods at the moment. In Python, you can define it as follows: ```python class Thing: pass ```

Print the Class

Print the class `Thing` itself using the `print()` function. This will output the information about the class definition, not the contents of any instantiated object. Run: ```python print(Thing) ```

Create an Instance

Instantiate the class `Thing` to create an object named `example`. This is done by calling the class as though it were a function, as shown: ```python example = Thing() ```

Print the Object Instance

Print the object `example` using the `print()` function. This will display information about the instance, which is different from printing the class definition itself. Run: ```python print(example) ```

Compare Printed Outputs

Observe the printed outputs from Steps 2 and 4. The output from printing the class will differ from the output when printing an instance of the class as each refers to different Python objects. The class output will be something like ``, whereas the instance output will be similar to `<__main__.Thing object at some_memory_location>`, indicating a specific memory address.

Key concepts

Python classes

In Python, a class acts as a blueprint for creating objects. It's a fundamental part of object-oriented programming. A class defines the properties and behaviors that its objects will have. Consider it like a recipe that describes how to make a certain type of dish, specifying ingredients and steps. In the provided exercise, the class `Thing` was created without any content, meaning it had no properties or methods defined. Yet, it still exists as a class because it's a template ready to be instantiated.
If you think about a class as a mold, it doesn't contain any of the things you can make with it, but it holds the potential to create them. When you define a class using the `class` keyword in Python, you're establishing this mold.
Key points about classes in Python:

• They are templates used to create objects.
• Defined using the `class` keyword followed by the class name.
• Can contain attributes (variables) and methods (functions).
• They encapsulate data for the created objects.

Even when a class is empty like `Thing`, it's still a valid class definition in Python, fully capable of producing objects from it.

Python objects

Objects in Python are instances of classes. Think of an object as a particular realization of the class's mold, like a single car made from the car blueprint. When you create an object, you're taking the instructions from the class and producing something tangible that you can use in your program.
In the exercise, an object called `example` was created from the `Thing` class. Even though `Thing` was an empty class with no methods or attributes, `example` is still a valid object. This object now exists separately from the class definition and has its own place in the computer’s memory.
Some important characteristics of Python objects include:

• They are specific instances of a class.
• Created by calling a class as if it were a function.
• Each object can have its own data and operational behavior, if defined by the class.
• Stored in memory at an address, uniquely identified when printed, as in `<__main__.Thing object at some_memory_location>`.

Objects are how you interact with and manipulate data in an object-oriented program, allowing you to execute operations and access attributes defined in the class template.

Instance and class differentiation

The concept of instance and class differentiation is essential in understanding how Python's object-oriented programming structure works. It revolves around distinguishing between what is a class and what is an instance of that class, i.e., an object. When you define a class, you are not creating any tangible object; rather, you're defining a type or category of object. This is analogous to writing a script or a recipe before any actual cooking happens.
An instance, on the other hand, is the concrete manifestation of that class. It's the actual product of calling the class and encompasses individual data values and state. In the exercise, printing `Thing` gives a different output from printing `example`. `` when `Thing` is printed indicates the class definition, whereas `<__main__.Thing object at some_memory_location>` for `example` signifies a specific instance with its own memory location.
Key differentiation points are:

• Classes can be seen as general templates, while instances are specific objects created based on those templates.
• Printing a class will show the class's representation, while printing an instance will show its unique memory address.
• Instances can have their individual states, separate from any other instance of the same class.

Understanding this difference is crucial for effective object-oriented programming, as it sets the foundation for how data is structured and organized within the program.