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README.md

0x0C. Python - Almost a circle

Python OOP

Resources

Read or watch:

Requirements

Python Scripts

  • Allowed editors: vi, vim, emacs
  • All your files will be interpreted/compiled on Ubuntu 20.04 LTS using python3 (version 3.8.5)
  • All your files should end with a new line
  • The first line of all your files should be exactly #!/usr/bin/python3
  • A README.md file, at the root of the folder of the project, is mandatory
  • Your code should use the pycodestyle (version 2.8.*)
  • All your files must be executable
  • The length of your files will be tested using wc
  • All your modules should be documented: python3 -c 'print(__import__("my_module").__doc__)'
  • All your classes should be documented: python3 -c 'print(__import__("my_module").MyClass.__doc__)'
  • All your functions (inside and outside a class) should be documented: python3 -c 'print(__import__("my_module").my_function.__doc__)' and python3 -c 'print(__import__("my_module").MyClass.my_function.__doc__)'
  • A documentation is not a simple word, it’s a real sentence explaining what’s the purpose of the module, class or method (the length of it will be verified)

Python Unit Tests

  • Allowed editors: vi, vim, emacs
  • All your files should end with a new line
  • All your test files should be inside a folder tests
  • You have to use the unittest module
  • All your test files should be python files (extension: .py)
  • All your test files and folders should start with test_
  • Your file organization in the tests folder should be the same as your project: ex: for models/base.py, unit tests must be in: tests/test_models/test_base.py
  • All your tests should be executed by using this command: python3 -m unittest discover tests
  • You can also test file by file by using this command: python3 -m unittest tests/test_models/test_base.py
  • We strongly encourage you to work together on test cases so that you don’t miss any edge case

Tasks

0. If it's not tested it doesn't work

All your files, classes and methods must be unit tested and be PEP 8 validated.

guillaume@ubuntu:~/$ python3 -m unittest discover tests
...................................................................................
...................................................................................
.......................
----------------------------------------------------------------------
Ran 189 tests in 13.135s

OK
guillaume@ubuntu:~/$

Note that this is just an example. The number of tests you create can be different from the above example.

1. Base class

Write the first class Base:

Create a folder named models with an empty file __init__.py inside - with this file, the folder will become a Python package

Create a file named models/base.py:

  • Class Base:
    • private class attribute __nb_objects = 0
    • class constructor: def __init__(self, id=None)::
      • if id is not None, assign the public instance attribute id with this argument value - you can assume id is an integer and you don’t need to test the type of it
      • otherwise, increment __nb_objects and assign the new value to the public instance attribute id

This class will be the base of all other classes in this project. The goal of it is to manage id attribute in all your future classes and to avoid duplicating the same code (by extension, same bugs)

guillaume@ubuntu:~/$ cat 0-main.py
#!/usr/bin/python3
""" 0-main """
from models.base import Base

if __name__ == "__main__":

    b1 = Base()
    print(b1.id)

    b2 = Base()
    print(b2.id)

    b3 = Base()
    print(b3.id)

    b4 = Base(12)
    print(b4.id)

    b5 = Base()
    print(b5.id)

guillaume@ubuntu:~/$ ./0-main.py
1
2
3
12
4
guillaume@ubuntu:~/$

2. First Rectangle

Write the class Rectangle that inherits from Base:

  • In the file models/rectangle.py
  • Class Rectangle inherits from Base
  • Private instance attributes, each with its own public getter and setter:
    • __width -> width
    • __height -> height
    • __x -> x
    • __y -> y
  • Class constructor: def __init__(self, width, height, x=0, y=0, id=None):
    • Call the super class with id - this super call with use the logic of the __init__ of the Base class
    • Assign each argument width, height, x and y to the right attribute

Why private attributes with getter/setter? Why not directly public attribute?

Because we want to protect attributes of our class. With a setter, you are able to validate what a developer is trying to assign to a variable. So after, in your class you can “trust” these attributes.

guillaume@ubuntu:~/$ cat 1-main.py
#!/usr/bin/python3
""" 1-main """
from models.rectangle import Rectangle

if __name__ == "__main__":

    r1 = Rectangle(10, 2)
    print(r1.id)

    r2 = Rectangle(2, 10)
    print(r2.id)

    r3 = Rectangle(10, 2, 0, 0, 12)
    print(r3.id)

guillaume@ubuntu:~/$ ./1-main.py
1
2
12
guillaume@ubuntu:~/$

3. Validate attributes

Update the class Rectangle by adding validation of all setter methods and instantiation (id excluded):

  • If the input is not an integer, raise the TypeError exception with the message: <name of the attribute> must be an integer. Example: width must be an integer
  • If width or height is under or equals 0, raise the ValueError exception with the message: <name of the attribute> must be > 0. Example: width must be > 0
  • If x or y is under 0, raise the ValueError exception with the message: <name of the attribute> must be >= 0. Example: x must be >= 0
guillaume@ubuntu:~/$ cat 2-main.py
#!/usr/bin/python3
""" 2-main """
from models.rectangle import Rectangle

if __name__ == "__main__":

    try:
        Rectangle(10, "2")
    except Exception as e:
        print("[{}] {}".format(e.__class__.__name__, e))

    try:
        r = Rectangle(10, 2)
        r.width = -10
    except Exception as e:
        print("[{}] {}".format(e.__class__.__name__, e))

    try:
        r = Rectangle(10, 2)
        r.x = {}
    except Exception as e:
        print("[{}] {}".format(e.__class__.__name__, e))

    try:
        Rectangle(10, 2, 3, -1)
    except Exception as e:
        print("[{}] {}".format(e.__class__.__name__, e))

guillaume@ubuntu:~/$ ./2-main.py
[TypeError] height must be an integer
[ValueError] width must be > 0
[TypeError] x must be an integer
[ValueError] y must be >= 0
guillaume@ubuntu:~/$

4. Area first

Update the class Rectangle by adding the public method def area(self): that returns the area value of the Rectangle instance.

guillaume@ubuntu:~/$ cat 3-main.py
#!/usr/bin/python3
""" 3-main """
from models.rectangle import Rectangle

if __name__ == "__main__":

    r1 = Rectangle(3, 2)
    print(r1.area())

    r2 = Rectangle(2, 10)
    print(r2.area())

    r3 = Rectangle(8, 7, 0, 0, 12)
    print(r3.area())

guillaume@ubuntu:~/$ ./3-main.py
6
20
56
guillaume@ubuntu:~/$

5. Display #0

Update the class Rectangle by adding the public method def display(self): that prints in stdout the Rectangle instance with the character # - you don’t need to handle x and y here.

guillaume@ubuntu:~/$ cat 4-main.py
#!/usr/bin/python3
""" 4-main """
from models.rectangle import Rectangle

if __name__ == "__main__":

    r1 = Rectangle(4, 6)
    r1.display()

    print("---")

    r1 = Rectangle(2, 2)
    r1.display()

guillaume@ubuntu:~/$ ./4-main.py
####
####
####
####
####
####
---
##
##
guillaume@ubuntu:~/$

6. str

Update the class Rectangle by overriding the __str__ method so that it returns [Rectangle] (<id>) <x>/<y> - <width>/<height>

guillaume@ubuntu:~/$ cat 5-main.py
#!/usr/bin/python3
""" 5-main """
from models.rectangle import Rectangle

if __name__ == "__main__":

    r1 = Rectangle(4, 6, 2, 1, 12)
    print(r1)

    r2 = Rectangle(5, 5, 1)
    print(r2)

guillaume@ubuntu:~/$ ./5-main.py
[Rectangle] (12) 2/1 - 4/6
[Rectangle] (1) 1/0 - 5/5
guillaume@ubuntu:~/$

7. Display #1

Update the class Rectangle by improving the public method def display(self): to print in stdout the Rectangle instance with the character # by taking care of x and y

guillaume@ubuntu:~/$ cat 6-main.py
#!/usr/bin/python3
""" 6-main """
from models.rectangle import Rectangle

if __name__ == "__main__":

    r1 = Rectangle(2, 3, 2, 2)
    r1.display()

    print("---")

    r2 = Rectangle(3, 2, 1, 0)
    r2.display()

guillaume@ubuntu:~/$ ./6-main.py | cat -e
$
$
  ##$
  ##$
  ##$
---$
 ###$
 ###$
guillaume@ubuntu:~/$