100+ Python challenging programming exercises 6

Question 51

Define a class named American and its subclass NewYorker.

Hints: Use class Subclass(ParentClass) to define a subclass.

Solution:

class American:  
    def __init__(self, name, age):  
        self.name = name  
        self.age = age  
  
    def introduce(self):  
        return f"Hello, my name is {self.name} and I am {self.age} years old."  
  
class NewYorker(American):  
    def introduce(self):  
        return f"Yo, my name is {self.name} and I am from New York. I'm {self.age} years old."

anAmerican = American('Tom',8)
aNewYorker = NewYorker('Jerry',5)

print(anAmerican.introduce())
print(aNewYorker.introduce())

 Out:

Hello, my name is Tom and I am 8 years old.
Yo, my name is Jerry and I am from New York. I'm 5 years old.

Question 52

Define a class named Circle which can be constructed by a radius. The Circle class has a method which can compute the area.

Hints: Use def methodName(self) to define a method.

Solution:

class Circle(object):
    def __init__(self, r):
        self.radius = r

    def area(self):
        return self.radius**2*3.14

aCircle = Circle(10)
print(aCircle.area())

Out:

314.0

Question 53

Define a class named Rectangle which can be constructed by a length and width. The Rectangle class has a method which can compute the area.

Hints: Use def methodName(self) to define a method.

Solution:

class Rectangle(object):
    def __init__(self, l, w):
        self.length = l
        self.width = w

    def area(self):
        return self.length*self.width

aRectangle = Rectangle(3,5)
print(aRectangle.area())

Out:

15 

Question 54

Define a class named Shape and its subclass Square. The Square class has an init function which takes a length as argument. Both classes have a area function which can print the area of the shape where Shape's area is 0 by default.

Hints: To override a method in super class, we can define a method with the same name in the super class.

Solution:

class Shape(object):
     def __init__(self):
          pass

     def area(self):
          return 0

class Square(Shape):
     def __init__(self, l):
          Shape.__init__(self)
          self.length = l

     def area(self):
          return self.length*self.length

aSquare = Square(3)
print(aSquare.area())

Out:

9 

Question 55

Please raise a RuntimeError exception.

Hints: Use raise() to raise an exception.

Solution:

raise RuntimeError('something wrong')

Question 56

Write a function to compute 5/0 and use try/except to catch the exceptions.

Hints: Use try/except to catch exceptions.

Solution:

def throws():
     return 5/0

try:
     throws()
except ZeroDivisionError:
     print("division by zero!")
except Exception(err):
     print('Caught an exception')
finally:
     print('In finally block for cleanup')

Out:

division by zero!
In finally block for cleanup

Question 57

Define a custom exception class which takes a string message as attribute.

Hints: To define a custom exception, we need to define a class inherited from Exception.

Solution:

class CustomException(Exception):  
    def __init__(self, message):  
        self.message = message

try:  
    raise CustomException("This is a custom exception")  
except CustomException as e:  
    print(e.message) 

Out:

"This is a custom exception"

Question 58

Assuming that we have some email addresses in the "username@companyname.com" format, please write program to print the user name of a given email address. Both user names and company names are composed of letters only.

Example: If the following email address is given as input to the program:

john@google.com

Then, the output of the program should be:

john

In case of input data being supplied to the question, it should be assumed to be a console input.

Hints: Use \w to match letters.

Solution:

import re
emailAddress = input()
pat2 = "(\w+)@"
r2 = re.match(pat2,emailAddress)
print(r2.group(1))

In:
john@google.com

Out:
John

Question 59

Assuming that we have some email addresses in the "username@companyname.com" format, please write program to print the company name of a given email address. Both user names and company names are composed of letters only.

Example: If the following email address is given as input to the program:

john@google.com

Then, the output of the program should be:

google

In case of input data being supplied to the question, it should be assumed to be a console input.

Hints: Use \w to match letters.

Solution:

import re
emailAddress = input()
pat2 = "(\w+)@(\w+)\.(com)"
r2 = re.match(pat2,emailAddress)
print(r2.group(2))

In:
john@google.com

Out:
google

Question 60

Write a program which accepts a sequence of words separated by whitespace as input to print the words composed of digits only.

Example: If the following words is given as input to the program:

2 cats and 3 dogs.

Then, the output of the program should be:

['2', '3']

In case of input data being supplied to the question, it should be assumed to be a console input.

Hints: Use re.findall() to find all substring using regex.

Solution:

import re
s = input()
print(re.findall("\d+",s))

In:
2 cats and 3 dogs

Out:
['2', '3']

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