CodeStepByStep

This site requires JavaScript. It looks like you have disabled JavaScript in your browser or are using a browser that does not support JavaScript. Please enable it or try another browser.

< Calculator_class

Date >

Main Page → Exercises → Python → Solve an Exercise

class_concepts

Language/Type: Python recursion

Answer the following questions about classes and objects:

What is an object?
A function that calls itself. An entity that combines state and behavior. An object is a synonym for a program. An object is when a program crashes with an error. Any value in a program such as an int or string. (order shuffled)
How is an object different from a class?
A class is a template or blueprint for a new type, and an object is an instance of that type. Objects can only store data, while classes can also contain behavior (methods). They are the same; the terms are interchangeable. Python supports objects but does not support classes. An object is larger and more powerful than a class. (order shuffled)
What is the difference between object-oriented programming and procedural programming?
Python is a procedural language and does not allow object-oriented programming. Object-oriented programming is more powerful and able to solve more problems than procedural. Procedural programming treats a program as a sequence of actions or commands, and object-oriented programming looks at a program as a group of interacting objects. Object-oriented programming contains no simple values like ints, only objects. Procedural programs runs code in sequential order, while object-oriented programs run in random orders chosen by the objects. (order shuffled)
What is the difference between a parameter and a data attribute?
An attribute is stored inside of an object, while a parameter is passed in to a function. When making a class, data attributes are optional but parameters are required. Parameters are one type of data attribute. The other is a list. Parameters use a different syntax where you must specify a default value. Parameters use less memory than data attributes. (order shuffled)
What is the difference between an accessor and mutator method?
A mutator converts one type of object into another type of object. Accessors are public while mutators are private. An accessor provides access to an object's data, while a mutator changes the object's state. Accessors are normal methods (functions) and mutators are ones that are part of objects. An accessor requires that the caller request access before calling it. (order shuffled)
Suppose we have a class BankAccount with a method compute_interest(self, rate). What is the correct syntax to call this method on a variable named acct?
result = compute_interest(acct, 42) acct.compute_interest(42.0, 15) result = BankAccount.compute_interest(42) result = acct.compute_interest(42) BankAccount(42).compute_interest()
How do you write a class whose objects can easily be printed on the console?
Write a print method in the class. Write a __str__ method in the class. Use only data attributes of type string in the class. Comment the class thoroughly. Include a bool attribute, printable = True.
The following print statement is equivalent to which of the following? d1 = Date() ... print(d1)
print(__str__(d1)) d1.__str__() print(d1.__str__()) print(Date.__str__())
What is abstraction?
Declaring a method's heading but omitting the body of the method. The ability to focus on a problem at a high level without worrying about the minor details. Writing object-oriented code rather than procedural code. Writing pseudocode without implementing the actual program. Multiple classes providing the same functionality. (order shuffled)
How do objects provide abstraction?
The improved performance from objects makes programs faster, which makes them more abstract. They force us to split our programs into multiple files. By linking data and behavior without having to manage and manipulate the data directly. Methods are more secure than normal functions. Objects do not provide abstraction if the client can see their source code. (order shuffled)
When attributes are made private, client programs are not supposed to access them directly. How do you allow classes access to read these attributes' values, without letting the client break the object's encapsulation?
Raise an error that contains the object's state. Print the object's state to the console. Just let the client access the data attributes directly, since they are not actually private. Write the object's state out to a file, and let the client read from the file. Create properties that return their values. (order shuffled)
How does encapsulation make it easier to change the internal implementation of a class?
Clients do not directly access the attributes, so changing those fields will not disturb client behavior as long as the external view (method behavior) is consistent. Encapsulation allows you to call the change_implementation() method on the object. Encapsulated objects tend to be better documented, so if there is a change, the client will see it in the documentation and know to change their code. Encapsulation makes the class invisible to clients, so they cannot use it at all. Encapsulated objects do not have any data attributes, so there is no implementation to change. (order shuffled)
How can you tell whether a class is cohesive?
When it runs well in a text interface and/or graphical user interface. When it does not contain very many attributes or methods. When each of its attributes stores important state related to the object and each method interacts with that state in some way to produce useful behavior. When it has thorough documentation and comments. When it has high performance and runs quickly. (order shuffled)
Why is it often considered poor style to put console I/O code into a class?
Doing so forces clients to use a text interface with that class and forces them to use exactly the same messages in that interface. It can cause errors to be raised from the class's code. We cannot put I/O code in a class because the print() function does not have access to the 'self' parameter. It makes the class have poor runtime performance. (order shuffled)

Ad Blocker Detected

Main Page → Exercises → Python → Solve an Exercise

class_concepts