Resources

Read or watch:

Inheritance
Multiple inheritance
Inheritance in Python
Learn to Program 10 : Inheritance Magic Methods

Learning Objectives

At the end of this project, you are expected to be able to explain to anyone, without the help of Google:

General

Why Python programming is awesome
What is a superclass, baseclass or parentclass
What is a subclass
How to list all attributes and methods of a class or instance
When can an instance have new attributes
How to inherit class from another
How to define a class with multiple base classes
What is the default class every class inherit from
How to override a method or attribute inherited from the base class
Which attributes or methods are available by heritage to subclasses
What is the purpose of inheritance
What are, when and how to use isinstance, issubclass, type and super built-in functions

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

Python Test Cases

Allowed editors: vi, vim, emacs
All your files should end with a new line
All your test files should be inside a folder tests
All your test files should be text files (extension: .txt)
All your tests should be executed by using this command: python3 -m doctest ./tests/*
All your modules should have a documentation (python3 -c 'print(__import__("my_module").__doc__)')
All your classes should have a documentation (python3 -c 'print(__import__("my_module").MyClass.__doc__)')
All your functions (inside and outside a class) should have a documentation (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)
We strongly encourage you to work together on test cases, so that you don’t miss any edge case

Documentation

Do not use the words import or from inside your comments, the checker will think you try to import some modules

Quiz questions

Question #0

What do these lines print?

class Base():
    """ My base class """

    __nb_instances = 0

    def __init__(self):
        Base.__nb_instances += 1
        self.id = Base.__nb_instances

class User(Base):
    """ My User class """

    def __init__(self):
        self.id = 89
        super().__init__()

u = User()
print(u.id)

89
90
1

Question #1

What do these lines print?

class Base():
    """ My base class """

    __nb_instances = 0

    def __init__(self):
        Base.__nb_instances += 1
        self.id = Base.__nb_instances

class User(Base):
    """ My User class """

    def __init__(self):
        super().__init__()
        self.id = 89

u = User()
print(u.id)

89
90
1

Question #2

What do these lines print?

class Base():
    """ My base class """

    __nb_instances = 0

    def __init__(self):
        Base.__nb_instances += 1
        self.id = Base.__nb_instances

b = Base()
print(b.id)

None
0
1

Question #3

What do these lines print?

class Base():
    """ My base class """

    __nb_instances = 0

    def __init__(self):
        Base.__nb_instances += 1
        self.id = Base.__nb_instances

class User(Base):
    """ My User class """
    pass

for i in range(4):
    u = User()
print(u.id)

None
4
3
5

Question #4

What do these lines print?

class Base():
    """ My base class """

    __nb_instances = 0

    def __init__(self):
        Base.__nb_instances += 1
        self.id = Base.__nb_instances

for i in range(3):
    b = Base()
print(b.id)

2
None
3
4

Question #5

What do these lines print?

class Base():
    """ My base class """

    __nb_instances = 0

    def __init__(self):
        Base.__nb_instances += 1
        self.id = Base.__nb_instances

class User(Base):
    """ My User class """

    def __init__(self):
        super().__init__()
        self.id += 99

u = User()
print(u.id)

99
100
1

Question #6

What do these lines print?

class Base():
    """ My base class """

    __nb_instances = 0

    def __init__(self):
        Base.__nb_instances += 1
        self.id = Base.__nb_instances

class User(Base):
    """ My User class """
    pass

u = User()
print(u.id)

2
None
0
1

Question #7

What do these lines print?

class Base():
    """ My base class """

    __nb_instances = 0

    def __init__(self):
        Base.__nb_instances += 1
        self.id = Base.__nb_instances

class User(Base):
    """ My User class """
    pass

b = Base()
u = User()
print(u.id)

3
0
1
2

Question #8

What do these lines print?

class Base():
    """ My base class """

    __nb_instances = 0

    def __init__(self):
        Base.__nb_instances += 1
        self.id = Base.__nb_instances

class User(Base):
    """ My User class """

    def __init__(self):
        super().__init__()

u = User()
print(u.id)

2
None
0
1

Question #9

What do these lines print?

class Base():
    """ My base class """

    __nb_instances = 0

    def __init__(self):
        Base.__nb_instances += 1
        self.id = Base.__nb_instances

class User(Base):
    """ My User class """

    def __init__(self):
        self.id = 89

u = User()
print(u.id)

89
90
1

Tasks

0. Lookup

Write a function that returns the list of available attributes and methods of an object:

Prototype: def lookup(obj):
Returns a list object
You are not allowed to import any module

guillaume@ubuntu:~/0x0A$ cat 0-main.py
#!/usr/bin/python3
lookup = __import__('0-lookup').lookup

class MyClass1(object):
    pass

class MyClass2(object):
    my_attr1 = 3
    def my_meth(self):
        pass

print(lookup(MyClass1))
print(lookup(MyClass2))
print(lookup(int))

guillaume@ubuntu:~/0x0A$ ./0-main.py
['__class__', '__delattr__', '__dict__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__gt__', '__hash__', '__init__', '__le__', '__lt__', '__module__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', '__weakref__']
['__class__', '__delattr__', '__dict__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__gt__', '__hash__', '__init__', '__le__', '__lt__', '__module__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', '__weakref__', 'my_attr1', 'my_meth']
['__abs__', '__add__', '__and__', '__bool__', '__ceil__', '__class__', '__delattr__', '__dir__', '__divmod__', '__doc__', '__eq__', '__float__', '__floor__', '__floordiv__', '__format__', '__ge__', '__getattribute__', '__getnewargs__', '__gt__', '__hash__', '__index__', '__init__', '__int__', '__invert__', '__le__', '__lshift__', '__lt__', '__mod__', '__mul__', '__ne__', '__neg__', '__new__', '__or__', '__pos__', '__pow__', '__radd__', '__rand__', '__rdivmod__', '__reduce__', '__reduce_ex__', '__repr__', '__rfloordiv__', '__rlshift__', '__rmod__', '__rmul__', '__ror__', '__round__', '__rpow__', '__rrshift__', '__rshift__', '__rsub__', '__rtruediv__', '__rxor__', '__setattr__', '__sizeof__', '__str__', '__sub__', '__subclasshook__', '__truediv__', '__trunc__', '__xor__', 'bit_length', 'conjugate', 'denominator', 'from_bytes', 'imag', 'numerator', 'real', 'to_bytes']
guillaume@ubuntu:~/0x0A$

No test cases needed

Repo:

GitHub repository: alx-higher_level_programming
Directory: 0x0A-python-inheritance
File: 0-lookup.py

1. My list

Write a class MyList that inherits from list:

Public instance method: def print_sorted(self): that prints the list, but sorted (ascending sort)
You can assume that all the elements of the list will be of type int
You are not allowed to import any module

guillaume@ubuntu:~/0x0A$ cat 1-main.py
#!/usr/bin/python3
MyList = __import__('1-my_list').MyList

my_list = MyList()
my_list.append(1)
my_list.append(4)
my_list.append(2)
my_list.append(3)
my_list.append(5)
print(my_list)
my_list.print_sorted()
print(my_list)

guillaume@ubuntu:~/0x0A$ ./1-main.py
[1, 4, 2, 3, 5]
[1, 2, 3, 4, 5]
[1, 4, 2, 3, 5]
guillaume@ubuntu:~/0x0A$

Repo:

GitHub repository: alx-higher_level_programming
Directory: 0x0A-python-inheritance
File: 1-my_list.py, tests/1-my_list.txt

2. Exact same object

Write a function that returns True if the object is exactly an instance of the specified class ; otherwise False.

Prototype: def is_same_class(obj, a_class):
You are not allowed to import any module

guillaume@ubuntu:~/0x0A$ cat 2-main.py
#!/usr/bin/python3
is_same_class = __import__('2-is_same_class').is_same_class

a = 1
if is_same_class(a, int):
    print("{} is an instance of the class {}".format(a, int.__name__))
if is_same_class(a, float):
    print("{} is an instance of the class {}".format(a, float.__name__))
if is_same_class(a, object):
    print("{} is an instance of the class {}".format(a, object.__name__))

guillaume@ubuntu:~/0x0A$ ./2-main.py
1 is an instance of the class int
guillaume@ubuntu:~/0x0A$

No test cases needed

Repo:

GitHub repository: alx-higher_level_programming
Directory: 0x0A-python-inheritance
File: 2-is_same_class.py

3. Same class or inherit from

Write a function that returns True if the object is an instance of, or if the object is an instance of a class that inherited from, the specified class ; otherwise False.

Prototype: def is_kind_of_class(obj, a_class):
You are not allowed to import any module

guillaume@ubuntu:~/0x0A$ cat 3-main.py
#!/usr/bin/python3
is_kind_of_class = __import__('3-is_kind_of_class').is_kind_of_class

a = 1
if is_kind_of_class(a, int):
    print("{} comes from {}".format(a, int.__name__))
if is_kind_of_class(a, float):
    print("{} comes from {}".format(a, float.__name__))
if is_kind_of_class(a, object):
    print("{} comes from {}".format(a, object.__name__))

guillaume@ubuntu:~/0x0A$ ./3-main.py
1 comes from int
1 comes from object
guillaume@ubuntu:~/0x0A$

No test cases needed

Repo:

GitHub repository: alx-higher_level_programming
Directory: 0x0A-python-inheritance
File: 3-is_kind_of_class.py

4. Only sub class of

Write a function that returns True if the object is an instance of a class that inherited (directly or indirectly) from the specified class ; otherwise False.

Prototype: def inherits_from(obj, a_class):
You are not allowed to import any module

guillaume@ubuntu:~/0x0A$ cat 4-main.py
#!/usr/bin/python3
inherits_from = __import__('4-inherits_from').inherits_from

a = True
if inherits_from(a, int):
    print("{} inherited from class {}".format(a, int.__name__))
if inherits_from(a, bool):
    print("{} inherited from class {}".format(a, bool.__name__))
if inherits_from(a, object):
    print("{} inherited from class {}".format(a, object.__name__))

guillaume@ubuntu:~/0x0A$ ./4-main.py
True inherited from class int
True inherited from class object
guillaume@ubuntu:~/0x0A$

No test cases needed

Repo:

GitHub repository: alx-higher_level_programming
Directory: 0x0A-python-inheritance
File: 4-inherits_from.py

5. Geometry module

Write an empty class BaseGeometry.

You are not allowed to import any module

guillaume@ubuntu:~/0x0A$ cat 5-main.py
#!/usr/bin/python3
BaseGeometry = __import__('5-base_geometry').BaseGeometry

bg = BaseGeometry()

print(bg)
print(dir(bg))
print(dir(BaseGeometry))

guillaume@ubuntu:~/0x0A$ ./5-main.py
<5-base_geometry.BaseGeometry object at 0x7f2050c69208>
['__class__', '__delattr__', '__dict__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__gt__', '__hash__', '__init__', '__le__', '__lt__', '__module__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', '__weakref__']
['__class__', '__delattr__', '__dict__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__gt__', '__hash__', '__init__', '__le__', '__lt__', '__module__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', '__weakref__']
guillaume@ubuntu:~/0x0A$

No test cases needed

Repo:

GitHub repository: alx-higher_level_programming
Directory: 0x0A-python-inheritance
File: 5-base_geometry.py

6. Improve Geometry

Write a class BaseGeometry (based on 5-base_geometry.py).

Public instance method: def area(self): that raises an Exception with the message area() is not implemented
You are not allowed to import any module

guillaume@ubuntu:~/0x0A$ cat 6-main.py
#!/usr/bin/python3
BaseGeometry = __import__('6-base_geometry').BaseGeometry

bg = BaseGeometry()

try:
    print(bg.area())
except Exception as e:
    print("[{}] {}".format(e.__class__.__name__, e))

guillaume@ubuntu:~/0x0A$ ./6-main.py
[Exception] area() is not implemented
guillaume@ubuntu:~/0x0A$

No test cases needed

Repo:

GitHub repository: alx-higher_level_programming
Directory: 0x0A-python-inheritance
File: 6-base_geometry.py

7. Integer validator

Write a class BaseGeometry (based on 6-base_geometry.py).

Public instance method: def area(self): that raises an Exception with the message area() is not implemented
Public instance method: def integer_validator(self, name, value): that validates value:
- you can assume name is always a string
- if value is not an integer: raise a TypeError exception, with the message <name> must be an integer
- if value is less or equal to 0: raise a ValueError exception with the message <name> must be greater than 0
You are not allowed to import any module

guillaume@ubuntu:~/0x0A$ cat 7-main.py
#!/usr/bin/python3
BaseGeometry = __import__('7-base_geometry').BaseGeometry

bg = BaseGeometry()

bg.integer_validator("my_int", 12)
bg.integer_validator("width", 89)

try:
    bg.integer_validator("name", "John")
except Exception as e:
    print("[{}] {}".format(e.__class__.__name__, e))

try:
    bg.integer_validator("age", 0)
except Exception as e:
    print("[{}] {}".format(e.__class__.__name__, e))

try:
    bg.integer_validator("distance", -4)
except Exception as e:
    print("[{}] {}".format(e.__class__.__name__, e))

guillaume@ubuntu:~/0x0A$ ./7-main.py
[TypeError] name must be an integer
[ValueError] age must be greater than 0
[ValueError] distance must be greater than 0
guillaume@ubuntu:~/0x0A$

Repo:

GitHub repository: alx-higher_level_programming
Directory: 0x0A-python-inheritance
File: 7-base_geometry.py, tests/7-base_geometry.txt

8. Rectangle

Write a class Rectangle that inherits from BaseGeometry (7-base_geometry.py).

Instantiation with width and height: def __init__(self, width, height):
- width and height must be private. No getter or setter
- width and height must be positive integers, validated by integer_validator

guillaume@ubuntu:~/0x0A$ cat 8-main.py
#!/usr/bin/python3
Rectangle = __import__('8-rectangle').Rectangle

r = Rectangle(3, 5)

print(r)
print(dir(r))

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

try:
    r2 = Rectangle(4, True)
except Exception as e:
    print("[{}] {}".format(e.__class__.__name__, e))

guillaume@ubuntu:~/0x0A$ ./8-main.py
<8-rectangle.Rectangle object at 0x7f6f488f7eb8>
['_Rectangle__height', '_Rectangle__width', '__class__', '__delattr__', '__dict__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__gt__', '__hash__', '__init__', '__le__', '__lt__', '__module__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', '__weakref__', 'area', 'integer_validator']
[AttributeError] 'Rectangle' object has no attribute 'width'
[TypeError] height must be an integer
guillaume@ubuntu:~/0x0A$

No test cases needed

Repo:

GitHub repository: alx-higher_level_programming
Directory: 0x0A-python-inheritance
File: 8-rectangle.py

9. Full rectangle

Write a class Rectangle that inherits from BaseGeometry (7-base_geometry.py). (task based on 8-rectangle.py)

Instantiation with width and height: def __init__(self, width, height)::
- width and height must be private. No getter or setter
- width and height must be positive integers validated by integer_validator
the area() method must be implemented
print() should print, and str() should return, the following rectangle description: [Rectangle] <width>/<height>

guillaume@ubuntu:~/0x0A$ cat 9-main.py
#!/usr/bin/python3
Rectangle = __import__('9-rectangle').Rectangle

r = Rectangle(3, 5)

print(r)
print(r.area())

guillaume@ubuntu:~/0x0A$ ./9-main.py
[Rectangle] 3/5
15
guillaume@ubuntu:~/0x0A$

No test cases needed

Repo:

GitHub repository: alx-higher_level_programming
Directory: 0x0A-python-inheritance
File: 9-rectangle.py

10. Square #1

Write a class Square that inherits from Rectangle (9-rectangle.py):

Instantiation with size: def __init__(self, size)::
- size must be private. No getter or setter
- sizemust be a positive integer, validated byinteger_validator`
the area() method must be implemented

guillaume@ubuntu:~/0x0A$ cat 10-main.py
#!/usr/bin/python3
Square = __import__('10-square').Square

s = Square(13)

print(s)
print(s.area())

guillaume@ubuntu:~/0x0A$ ./10-main.py
[Rectangle] 13/13
169
guillaume@ubuntu:~/0x0A$

No test cases needed

Repo:

GitHub repository: alx-higher_level_programming
Directory: 0x0A-python-inheritance
File: 10-square.py

11. Square #2

Write a class Square that inherits from Rectangle (9-rectangle.py). (task based on 10-square.py).

Instantiation with size: def __init__(self, size)::
- size must be private. No getter or setter
- size must be a positive integer, validated by integer_validator
the area() method must be implemented
print() should print, and str() should return, the square description: [Square] <width>/<height>

guillaume@ubuntu:~/0x0A$ cat 11-main.py
#!/usr/bin/python3
Square = __import__('11-square').Square

s = Square(13)

print(s)
print(s.area())

guillaume@ubuntu:~/0x0A$ ./11-main.py
[Square] 13/13
169
guillaume@ubuntu:~/0x0A$

No test cases needed

Repo:

GitHub repository: alx-higher_level_programming
Directory: 0x0A-python-inheritance
File: 11-square.py

12. My integer

Write a class MyInt that inherits from int:

MyInt is a rebel. MyInt has == and != operators inverted
You are not allowed to import any module

guillaume@ubuntu:~/0x0A$ cat 100-main.py
#!/usr/bin/python3
MyInt = __import__('100-my_int').MyInt

my_i = MyInt(3)
print(my_i)
print(my_i == 3)
print(my_i != 3)

guillaume@ubuntu:~/0x0A$ ./100-main.py
3
False
True
guillaume@ubuntu:~/0x0A$

No test cases needed

Repo:

GitHub repository: alx-higher_level_programming
Directory: 0x0A-python-inheritance
File: 100-my_int.py

13. Can I?

Write a function that adds a new attribute to an object if it’s possible:

Raise a TypeError exception, with the message can't add new attribute if the object can’t have new attribute
You are not allowed to use try/except
You are not allowed to import any module

guillaume@ubuntu:~/0x0A$ cat 101-main.py
#!/usr/bin/python3
add_attribute = __import__('101-add_attribute').add_attribute

class MyClass():
    pass

mc = MyClass()
add_attribute(mc, "name", "John")
print(mc.name)

try:
    a = "My String"
    add_attribute(a, "name", "Bob")
    print(a.name)
except Exception as e:
    print("[{}] {}".format(e.__class__.__name__, e))

guillaume@ubuntu:~/0x0A$ ./101-main.py
John
[TypeError] can't add new attribute
guillaume@ubuntu:~/0x0A$

No test cases needed

Repo:

GitHub repository: alx-higher_level_programming
Directory: 0x0A-python-inheritance
File: 101-add_attribute.py

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README.md

README.md

Resources

Learning Objectives

General

Requirements

Python Scripts

Python Test Cases

Documentation

Quiz questions

Question #0

Question #1

Question #2

Question #3

Question #4

Question #5

Question #6

Question #7

Question #8

Question #9

Tasks

0. Lookup

1. My list

2. Exact same object

3. Same class or inherit from

4. Only sub class of

5. Geometry module

6. Improve Geometry

7. Integer validator

8. Rectangle

9. Full rectangle

10. Square #1

11. Square #2

12. My integer

13. Can I?

Files

README.md

Latest commit

History

README.md

File metadata and controls

Resources

Learning Objectives

General

Requirements

Python Scripts

Python Test Cases

Documentation

Quiz questions

Question #0

Question #1

Question #2

Question #3

Question #4

Question #5

Question #6

Question #7

Question #8

Question #9

Tasks

0. Lookup

1. My list

2. Exact same object

3. Same class or inherit from

4. Only sub class of

5. Geometry module

6. Improve Geometry

7. Integer validator

8. Rectangle

9. Full rectangle

10. Square #1

11. Square #2

12. My integer

13. Can I?