Composition
Related code
class Family:
"""Represents a family."""
class Person:
"""Represents a person."""
We can compose class instances and their attributes with any other construct or data structure.
Value of an attribute can be a list:
... f = Family() f.name = "Krasniqi" f.members = ["Ali", "Bastrie"]
Class instances can be list items:
... p1, p2 = Person(), Person() p1.name, p2.name = "Ali", "Bastrie" f.members = [p1, p2]
f.members is a list, to which all list operations and methods can be applied:
... p3 = Person() p3.name = "Amire" f.members.append(p3)
>>> f.members [<Person object at 0x0000015E227D8CD0>, <Person object at 0x0000015E22F49010>, <Person object at 0x0000015E22F4A550>] >>> f.members[1].name Bastrie
Here is an example of a dictionary where its values are Person instances:
...
>>> members = {'p1': Person(), 'p2': Person()}
>>> members['p1'].name = "Maksut"
>>> members['p2'].name = "Maksute"
>>> p1 = members['p1']
>>> p1.name
Maksut
Exercises
Create two companies, add an employees: set attribute and add some employees to each of the companies.
Create a library, library and add some books to library.books dictionary
whose keys are characters and values are list of books whose title start with that character.
Example:
{'a': [<Book whose title is 'Ali baba'>, ...], 'o': [<Book whose title is 'Of Mice and Men'>, ...]}
Create three passengers and assign a name to each.
Create a flight and add some passengers to its passengers: list attribute.
Create four products and assign a name and a price to each.
Create two markets and add some products to their products: list attribute.
class Hospital:
pass
class Doctor:
pass
d1, d2 = Doctor(), Doctor()
d1.name, d2.name = "Dr. Liri", "Dr. Mirlinda"
h = Hospital()
h.staff = {"cardiology": d1, "urologji": d2}
print(h.staff["urologji"].name)
What is printed when we execute the above script
Exercises
Create two classes, School and Student.
Create a school and add some students to its students: list attribute.
Add one more student to school.
Create two classes, Recipe and Ingredient.
Create some ingredients with one attribute, name.
Create a recipe and add created ingredients to its ingredients: tuple attribute.
Print the name of the first ingredient of the created recipe.
Create two classes, Zoo and Animal.
Create some animals with one attribute, name.
Create a zoo and add created animals to its animals: set attribute.
Add one more animal to the zoo.
Create two classes, Concert and Performer.
Create some performers with one attribute, name.
Create a concert and add created performers to its performers: list attribute.
Print names of all concert performers
class Bakery:
pass
class Cake:
pass
c1, c2 = Cake(), Cake()
c1.name, c2.name = "Chocolate", "Vanilla"
b = Bakery()
b.cakes = [c1, c2]
c = b.cakes.pop(-1)
print(c.name)
What is printed when we execute the above script