So I have struggled with classes and objects but think I’m starting to get it…? As part of a short online class I made a program that asked a few multiple choice questions and returns a score. To do this there are a few parts.

  1. Define some inputs as lists of strings ((q, a), (q2, a2),…). The lists contain the questions and answers. This will be used as input and allows an easy way to change questions, add them, whatever.

  2. Create a class that takes in the list and creates objects - the objects are a question and it’s answer.

  3. Create a new list that uses that class to store the objects.

  4. Define a function that iterates over the list full of question/answer objects, and then asks the user the questions and tallies the score.

Number 2 is really what I am wondering about, is that generally what a class and object are? I would use an analogy of a factory being a class. It takes in raw materials (or pre-made parts) and builds them into standard objects. Is this a reasonable analogy of what a class is?

  • Em Adespoton@lemmy.ca
    2·
    3 months ago

    You are taking a short online class. The class has objectives.

    The class itself is defined by what it is supposed to handle (students mastering X skills). But the class by itself is only a structure, a definition that can be used to standardize ehat this sourt of course will look like. Within that class are actual students producing work that is more or less in line with the class objectives. These are objects that belong to the class that contain work.

    A class is the structured definition. So you could have a class “factory” that defines a factory as a large building that takes in raw materials and outputs a specific type of finished goods.

    The automotive factory on Fifth would be an object in the Factory class. That factory itself would be populated with contents defined by how the factory was operating.

    Likewise in Python, you can define a class Greeting that contains a single string. You can then define an object friendlyGreeting of type Greeting, and that object will automatically contain a single string, because that’s what objects of class Greeting have. You can then populate the string in friendlyGreeting with the characters “Hello World” and you have an instantiated object. You could then have another object inheriting Greeting named unfriendlyGreeting. It will also inherit the single string element. But if you never instantiate unfriendlyGreeting, it won’t be usable in your program, and will have no actual contents.

    So to sum up, classes define the structure of objects you use in your program. Objects define specific “things” that you can make copies of and interact with in your program. When an object is actually used and is containing data to be used in a specific way in your program, it is instantiated (there is an actual instance of that object).