0x08-python-more_classes

0x08. Python - More Classes and Objects

0. Simple rectangle mandatory

Write an empty class Rectangle that defines a rectangle:

• You are not allowed to import any module

1. Real definition of a rectangle mandatory

Write a class Rectangle that defines a rectangle by: (based on 0-rectangle.py)

• Private instance attribute: width:
  • property def width(self): to retrieve it
  • property setter def width(self, value): to set it:
    • width must be an integer, otherwise raise a TypeError exception with the message width must be an integer
      
    • if width is less than 0, raise a ValueError exception with the message width must be >= 0
• Private instance attribute: height:
  • property def height(self): to retrieve it
  • property setter def height(self, value): to set it:
    • height must be an integer, otherwise raise a TypeError exception with the message height must be an integer
      
    • if height is less than 0, raise a ValueError exception with the message height must be >= 0
• Instantiation with optional width and height: def __init__(self, width=0, height=0):
• You are not allowed to import any module

2. Area and Perimeter mandatory

Write a class Rectangle that defines a rectangle by: (based on 1-rectangle.py)

• Private instance attribute: width:
  • property def width(self): to retrieve it
  • property setter def width(self, value): to set it:
    • width must be an integer, otherwise raise a TypeError exception with the message width must be an integer
      
    • if width is less than 0, raise a ValueError exception with the message width must be >= 0
• Private instance attribute: height:
  • property def height(self): to retrieve it
  • property setter def height(self, value): to set it:
    • height must be an integer, otherwise raise a TypeError exception with the message height must be an integer
      
    • if height is less than 0, raise a ValueError exception with the message height must be >= 0
• Instantiation with optional width and height: def __init__(self, width=0, height=0):
• Public instance method: def area(self): that returns the rectangle area
• Public instance method: def perimeter(self): that returns the rectangle perimeter:
  • if width or height is equal to 0, perimeter is equal to 0
• You are not allowed to import any module

3. String representation mandatory

Write a class Rectangle that defines a rectangle by: (based on 2-rectangle.py)

• Private instance attribute: width:
  • property def width(self): to retrieve it
  • property setter def width(self, value): to set it:
    • width must be an integer, otherwise raise a TypeError exception with the message width must be an integer
      
    • if width is less than 0, raise a ValueError exception with the message width must be >= 0
• Private instance attribute: height:
  • property def height(self): to retrieve it
  • property setter def height(self, value): to set it:
    • height must be an integer, otherwise raise a TypeError exception with the message height must be an integer
      
    • if height is less than 0, raise a ValueError exception with the message height must be >= 0
• Instantiation with optional width and height: def __init__(self, width=0, height=0):
• Public instance method: def area(self): that returns the rectangle area
• Public instance method: def perimeter(self): that returns the rectangle perimeter:
  • if width or height is equal to 0, perimeter has to be equal to 0
• print() and str() should print the rectangle with the character #: (see example below)
  • if width or height is equal to 0, return an empty string
• You are not allowed to import any module

4. Eval is magic mandatory

Write a class Rectangle that defines a rectangle by: (based on 3-rectangle.py)

• Private instance attribute: width:
  • property def width(self): to retrieve it
  • property setter def width(self, value): to set it:
    • width must be an integer, otherwise raise a TypeError exception with the message width must be an integer
      
    • if width is less than 0, raise a ValueError exception with the message width must be >= 0
• Private instance attribute: height:
  • property def height(self): to retrieve it
  • property setter def height(self, value): to set it:
    • height must be an integer, otherwise raise a TypeError exception with the message height must be an integer
      
    • if height is less than 0, raise a ValueError exception with the message height must be >= 0
• Instantiation with optional width and height: def __init__(self, width=0, height=0):
• Public instance method: def area(self): that returns the rectangle area
• Public instance method: def perimeter(self): that returns the rectangle perimeter:
  • if width or height is equal to 0, perimeter has to be equal to 0
• print() and str() should print the rectangle with the character #: (see example below)
  • if width or height is equal to 0, return an empty string
• repr() should return a string representation of the rectangle to be able to recreate a new instance by using eval() (see example below)
• You are not allowed to import any module

5. Detect instance deletion mandatory

Write a class Rectangle that defines a rectangle by: (based on 4-rectangle.py)

• Private instance attribute: width:
  • property def width(self): to retrieve it
  • property setter def width(self, value): to set it:
    • width must be an integer, otherwise raise a TypeError exception with the message width must be an integer
      
    • if width is less than 0, raise a ValueError exception with the message width must be >= 0
• Private instance attribute: height:
  • property def height(self): to retrieve it
  • property setter def height(self, value): to set it:
    • height must be an integer, otherwise raise a TypeError exception with the message height must be an integer
      
    • if height is less than 0, raise a ValueError exception with the message height must be >= 0
• Instantiation with optional width and height: def __init__(self, width=0, height=0):
• Public instance method: def area(self): that returns the rectangle area
• Public instance method: def perimeter(self): that returns the rectangle perimeter:
  • if width or height is equal to 0, perimeter has to be equal to 0
• print() and str() should print the rectangle with the character #:
  • if width or height is equal to 0, return an empty string
• repr() should return a string representation of the rectangle to be able to recreate a new instance by using eval()
• Print the message “Bye rectangle…” when an instance of Rectangle is deleted
• You are not allowed to import any module

6. How many instances mandatory

Write a class Rectangle that defines a rectangle by: (based on 5-rectangle.py)

• Private instance attribute: width:
  • property def width(self): to retrieve it
  • property setter def width(self, value): to set it:
    • width must be an integer, otherwise raise a TypeError exception with the message width must be an integer
      
    • if width is less than 0, raise a ValueError exception with the message width must be >= 0
• Private instance attribute: height:
  • property def height(self): to retrieve it
  • property setter def height(self, value): to set it:
    • height must be an integer, otherwise raise a TypeError exception with the message height must be an integer
      
    • if height is less than 0, raise a ValueError exception with the message height must be >= 0
• Public class attribute number_of_instances:
  • Initialized to 0
  • Incremented during each new instance instantiation
  • Decremented during each instance deletion
• Instantiation with optional width and height: def __init__(self, width=0, height=0):
• Public instance method: def area(self): that returns the rectangle area
• Public instance method: def perimeter(self): that returns the rectangle perimeter:
  • if width or height is equal to 0, perimeter has to be equal to 0
• print() and str() should print the rectangle with the character #:
  • if width or height is equal to 0, return an empty string
• repr() should return a string representation of the rectangle to be able to recreate a new instance by using eval()
• Print the message “Bye rectangle…” when an instance of Rectangle is deleted
• You are not allowed to import any module

7. Change representation mandatory

Write a class Rectangle that defines a rectangle by: (based on 6-rectangle.py)

• Private instance attribute: width:
  • property def width(self): to retrieve it
  • property setter def width(self, value): to set it:
    • width must be an integer, otherwise raise a TypeError exception with the message width must be an integer
      
    • if width is less than 0, raise a ValueError exception with the message width must be >= 0
• Private instance attribute: height:
  • property def height(self): to retrieve it
  • property setter def height(self, value): to set it:
    • height must be an integer, otherwise raise a TypeError exception with the message height must be an integer
      
    • if height is less than 0, raise a ValueError exception with the message height must be >= 0
• Public class attribute number_of_instances:
  • Initialized to 0
  • Incremented during each new instance instantiation
  • Decremented during each instance deletion
• Public class attribute print_symbol:
  • Initialized to #
  • Used as symbol for string representation
  • Can be any type
• Instantiation with optional width and height: def __init__(self, width=0, height=0):
• Public instance method: def area(self): that returns the rectangle area
• Public instance method: def perimeter(self): that returns the rectangle perimeter:
  • if width or height is equal to 0, perimeter has to be equal to 0
• print() and str() should print the rectangle with the character #:
  • if width or height is equal to 0, return an empty string
• repr() should return a string representation of the rectangle to be able to recreate a new instance by using eval()
• Print the message “Bye rectangle…” when an instance of Rectangle is deleted
• You are not allowed to import any module

8. Compare rectangles mandatory

Write a class Rectangle that defines a rectangle by: (based on 7-rectangle.py)

• Private instance attribute: width:
  • property def width(self): to retrieve it
  • property setter def width(self, value): to set it:
    • width must be an integer, otherwise raise a TypeError exception with the message width must be an integer
      
    • if width is less than 0, raise a ValueError exception with the message width must be >= 0
• Private instance attribute: height:
  • property def height(self): to retrieve it
  • property setter def height(self, value): to set it:
    • height must be an integer, otherwise raise a TypeError exception with the message height must be an integer
      
    • if height is less than 0, raise a ValueError exception with the message height must be >= 0
• Public class attribute number_of_instances:
  • Initialized to 0
  • Incremented during each new instance instantiation
  • Decremented during each instance deletion
• Public class attribute print_symbol:
  • Initialized to #
  • Used as symbol for string representation
  • Can be any type
• Instantiation with optional width and height: def __init__(self, width=0, height=0):
• Public instance method: def area(self): that returns the rectangle area
• Public instance method: def perimeter(self): that returns the rectangle perimeter:
  • if width or height is equal to 0, perimeter has to be equal to 0
• print() and str() should print the rectangle with the character #:
  • if width or height is equal to 0, return an empty string
• repr() should return a string representation of the rectangle to be able to recreate a new instance by using eval()
• Print the message “Bye rectangle…” when an instance of Rectangle is deleted
• Static method def bigger_or_equal(rect_1, rect_2): that returns the biggest rectangle based on the area
  • rect_1 must be an instance of Rectangle, otherwise raise a TypeError exception with the message rect_1 must be an instance of Rectangle
    
  • rect_2 must be an instance of Rectangle, otherwise raise a TypeError exception with the message rect_2 must be an instance of Rectangle
    
  • Returns rect_1 if both have the same area value
• You are not allowed to import any module

9. A square is a rectangle mandatory

Write a class Rectangle that defines a rectangle by: (based on 8-rectangle.py)

• Private instance attribute: width:
  • property def width(self): to retrieve it
  • property setter def width(self, value): to set it:
    • width must be an integer, otherwise raise a TypeError exception with the message width must be an integer
      
    • if width is less than 0, raise a ValueError exception with the message width must be >= 0
• Private instance attribute: height:
  • property def height(self): to retrieve it
  • property setter def height(self, value): to set it:
    • height must be an integer, otherwise raise a TypeError exception with the message height must be an integer
      
    • if height is less than 0, raise a ValueError exception with the message height must be >= 0
• Public class attribute number_of_instances:
  • Initialized to 0
  • Incremented during each new instance instantiation
  • Decremented during each instance deletion
• Public class attribute print_symbol:
  • Initialized to #
  • Used as symbol for string representation
  • Can be any type
• Instantiation with optional width and height: def __init__(self, width=0, height=0):
• Public instance method: def area(self): that returns the rectangle area
• Public instance method: def perimeter(self): that returns the rectangle perimeter:
  • if width or height is equal to 0, perimeter has to be equal to 0
• print() and str() should print the rectangle with the character #:
  • if width or height is equal to 0, return an empty string
• repr() should return a string representation of the rectangle to be able to recreate a new instance by using eval()
• Print the message “Bye rectangle…” when an instance of Rectangle is deleted
• Static method def bigger_or_equal(rect_1, rect_2): that returns the biggest rectangle based on the area
  • rect_1 must be an instance of Rectangle, otherwise raise a TypeError exception with the message rect_1 must be an instance of Rectangle
    
  • rect_2 must be an instance of Rectangle, otherwise raise a TypeError exception with the message rect_2 must be an instance of Rectangle
    
  • Returns rect_1 if both have the same area value
• Class method def square(cls, size=0): that returns a new Rectangle instance with width == height == size
• You are not allowed to import any module

10. Class and instance attributes #advanced

Write a blog post describing how object and class attributes work.

• What’s a class attribute
• What’s an instance attribute
• What are all the way to create them and what is the Pythonic way of doing it
• What are the differences between class and instance attributes
• What are the advantages and drawbacks of each of them
• How does Python deal with the object and class attributes using the __dic__

Your posts should have examples and at least one picture, at the top. Publish your blog post on Medium or LinkedIn, and share it at least on Twitter and LinkedIn.

When done, please add all urls below (blog post, tweet, etc.)

Add URLs here:

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11. N queens #advanced

Chess grandmaster Judit Polgár, the strongest female chess player of all time

The N queens puzzle is the challenge of placing N non-attacking queens on an N×N chessboard. Write a program that solves the N queens problem.

• Usage: nqueens N
  • If the user called the program with the wrong number of arguments, print Usage: nqueens N, followed by a new line, and exit with the status 1
• where N must be an integer greater or equal to 4
  • If N is not an integer, print N must be a number, followed by a new line, and exit with the status 1
  • If N is smaller than 4, print N must be at least 4, followed by a new line, and exit with the status 1
• The program should print every possible solution to the problem
  • One solution per line
  • Format: see example
  • You don’t have to print the solutions in a specific order
• You are only allowed to import the sys module

Read: Queen, Backtracking