Problem 4: Pretty Printer (100pts)

Part 1

Your first task is to define pretty printer methods for Pet, Cat and NoisyCat.

We start with implementing functions named to_str for Pet, Cat, and NoisyCat classes.

For Pet, the output should be:

>>> kyubey = Pet('Kyubey', 'Incubator')
>>> kyubey.to_str()
'(Kyubey, Incubator)'

For Cat and NoisyCat, the output should be:

>>> vanilla = Cat('Vanilla', 'Minazuki Kashou')
>>> vanilla.to_str()
'(Vanilla, Minazuki Kashou, 9)'
>>> vanilla.lose_life()
>>> vanilla.to_str()
'(Vanilla, Minazuki Kashou, 8)'

Now, we could define a function pretty_print, which accepts an object and print it prettily (i.e. with color).

To colorfully print something in terminal, this simplest way is to use ANSI escape code.

class Colors:
 HEADER     = '\033[95m'
 OKBLUE     = '\033[34m'
 OKCYAN     = '\033[35m'
 OKGREEN    = '\033[96m'
 WARNING    = '\033[93m'
 FAIL       = '\033[91m'
 ENDC       = '\033[0m'
 BOLD       = '\033[1m'
 UNDERLINE  = '\033[4m'


>>> print(f"{Colors.OKBLUE}Hello, World{Colors.ENDC}")
Hello, World # this line should be blue
>>> print(f"{Colors.OKCYAN}Hello, World{Colors.ENDC}")
Hello, World # this line should be red
>>> print(f"{Colors.UNDERLINE}Hello, World{Colors.ENDC}")
Hello, World # this line should be underlined

Windows Console may not be able to display that. Use vscode console or windows terminal instead.

For real world program, you should use a library to display colorful output. E.g. termcolor

pretty_print should print object with form type(to_str). The type is the class name of the input object, the to_str is the return value of object.to_str(). For example:

>>> kyubey = Pet('Kyubey', 'Incubator')
>>> pretty_print(kyubey)
Pet(Kyubey, Incubator)

example

We ignore the ascii escape code in examples, you can check the real output in doctest

Note:

  • type could be obtained by python builtin type(obj).__name__. E.g. type(kyubey).__name__ is Pet
  • The type part of the printed str should be displayed with color defined by Colors.OKBLUE. For most device/terminal, this color should be blue.
  • The to_str part of the printed str should be displayed with color defined by Colors.OKCYAN. For most device/terminal, this color should be like red.

Part 2

Your second task is to inject the defined pretty_print method to all Pet, Cat and NoisyCat classes. For example:

>>> kyubey = Pet('Kyubey', 'Incubator')
>>> kyubey.pp() # the same result as `pretty_print`
Pet(Kyubey, Incubator)

To smoothly support such method call, edit the declaration of the Pet class.

Hint1: You may not need to edit more than one line of code for this task.

Hint2: You should use the provided PrintModule class.

Test your code using python -i lab06.py with:

>>> kyubey = Pet('Kyubey', 'Incubator')
>>> kyubey.pp()
Pet(Kyubey, Incubator)
>>> vanilla = Cat('Vanilla', 'Minazuki Kashou')
>>> vanilla.pp()
Cat(Vanilla, Minazuki Kashou, 9)

This is an ugly implementation of mixin. You can check this page for ruby style mixin, which is clear and elegant.