Python Online Quiz Part 2 on Classes and Objects

If you enjoy getting through the coding problems, then you must attempt this Python online quiz. It packages 21 coding snippets focussing on Python classes.

Contents

With this quiz, you can quickly assess the technical depth of your Python programming ability.

Quiz on Python Classes and Objects

Those who are beginners and learning object-oriented programming should attempt this quiz on Python classes for beginners that we delivered a while ago.

Before diving into the quiz, let’s quickly know how to deal with Python classes. Though, you can use the below TOC to navigate to different sections of the post.

Create a class in Python

Python entitles the class keyword to produce a new class definition. Within a class, you can add member variables and methods. Here are a few facts about the accessibility.

Public

All members of a class are public by default in Python.

class ClipBoard:
    def __init__(self):
        self.target = None
        self.message = None

    def fill(self, text):
        self.message = text

    def clear(self):
        self.message = None

Now, you have a class ClipBoard. Following operations, you can do with it.

msWord = ClipBoard()
msWord.target = "MSWORD"
msWord.message = "Hello, World!"
msWord.clear()
msWord.fill("Any Text")

Protected

Unlike C++/Java, which supports protected members by design, Python allows implementing it by convention. Using underscore (_) as a prefix to any member, you mark it as protected.

Python doesn’t hold you from using a protected member. But it gives a symbolic way of doing that.

class ClipBoard:
    def __init__(self):
        self.target = None
        self._message = None # protected data

    def fill(self, text):
        self._message = text

    def clear(self):
        self._message = None

Private

You can use the name mangling technique to define a member as private in Python. It changes the way we usually access a class member. It states that if a member name begins with two underscores, then access the member in the following manner.

_<className><memberName>

class ClipBoard:
    def __init__(self, target):
        self.target = target
        self.__message = None # private data

    def fill(self, text):
        self.__message = text

    def clear(self):
        self.__message = None

To access the private member, you can do the following.

msWord = ClipBoard("MSWORD")
msWord._ClipBoard__message = "Any Text"

If you use a private member differently, then Python will throw an error.

Next, Python provides a set of built-in class attributes which you should know.

Built-in Class Attributes

Python inculcates a lot of other features in classes. It does so with the help of a number of built-in attributes.

1. __doc__ – It returns None by default or the doc string if set already.

2. __module__ – It’s the name of the target module containing the class definition.

3. __name__ – Name of the class.

4. __dict__ – Represents the dictionary referencing to the class’s namespace in Python.

5. __bases__ – Mostly, it’s an empty Python tuple holding an ordered list of base classes.

Next, let’s have a look at the concept of inheritance in Python.

Inheritance in Python

You don’t need a keyword to set up an inheritance for a class in Python. See how easy it is to prepare a derived class.

class MyDerivedClass(MyBaseClass):
    pass

Let’s now extend the ClipBoard class, please see the below example.

class ExtendedClipBoard(ClipBoard):
    def __init__(self, target, message):
        ClipBoard.target = target
        ClipBoard.message = message
        self.store = None

    def save(self):
        self.store = ClipBoard.target + ClipBoard.message

    def remove(self):
        self.store = None

Now, use the below instructions to test our derived and base classes.

obj = ExtendedClipBoard("MSOutlook", "Email")
obj.save()
print(obj.store)
obj.remove()
print(obj.store)

When you club the above coding snippets and run the code, it’ll return the following output.

Python 2.7.10 (default, Jul 14 2015, 19:46:27)
[GCC 4.8.2] on linux
   
MSOutlook Email
None

Overriding

Yes, you can override the parent class methods and modify their functionality. Also, you can override operators like +,-, and a list of generic class methods.

Here is a list of generic methods that you can override.

__init__ ( self [,args...] )
Constructor (supports optional arguments).
Example : object = className(args)

__del__( self )
Destructor (destroys an object).
Example : del object

__str__( self )
Computes the printable string representation.
Example : str(object)

__repr__( self )
Computes the "official" string representation.
Example : repr(object)

__cmp__ ( self, x )
Performs object comparison.
Example : cmp(object, result)

We hope the brief intro to Python classes above will help. Now, it’s time to turn on the Python online quiz’s start button.

Python Online Quiz – 21 Questions for Experienced Programmers

Q-1. What will be the output of the following code?

class Test:
     def __init__(self, s):
         self.s = s
 
     def print(self):
         print(s)

a = Test("Python Class")
a.print()

A. The program gives an error because there is no constructor for class Test.
B. The signature for the print method is incorrect, so an error is thrown.
C. The correct output is “Python Class”.
D. The above code will execute correctly on changing print(s) to print(self.s).