Instances as return value
Related code
class Dog:
"""Represents a dog.
attributes: name, age and collar
"""
class Collar:
"""Represents a collar.
attributes: color and size
"""
def print_dog_info(dog):
print(f"Name: {dog.name}, age: {dog.age}")
print(f"{dog.name}'s collar color: {dog.collar.color}, {dog.name}'s collar size: {dog.collar.size}")
Functions can return instances. For example, create_collar takes a color and a size, and returns a collar of such color and size:
...
def create_collar(color, size):
c = Collar()
c.color = color
c.size = size
return c
Here is an example of its usage:
...
dog = Dog()
dog.name, dog.age, dog.collar = "Murki", 2, create_collar('black', 5)
create_collar('black', 5) returned a Collar instance, and it was directly
assigned to dog's collar attribute.
>>> dog.collar
<Collar object at 0x00000148DF62B2D0>
>>> dog.collar.color, dog.collar.size
('black', 5)
>>>
Exercises
class Cow:
"""Represents a cow"""
class Robot:
"""Represents a robot"""
def print_robot_cow(robot):
print("name: {}, pet's name: {}".format(robot.name, robot.pet.name))
print("{}'s pet is {} years old.".format(robot.name, robot.pet.age))
Define a function, create_cow, which takes one string and one integer, name and age, creates a Cow object, assigns name to object's name attribute and age to object's age attribute, and returns the object
Create a robot, robot3, and add name attribute to it, which is a string representing robot's name
Call create_cow, passing the required arguments, and assign it's return value (directly) to pet attribute of robot3
Call create_author, passing the required arguments, and assign it's return value directly to author attribute of created book
class Bus:
pass
class Driver:
pass
def assign_driver(name):
d = Driver()
d.name = name
return d
b = Bus()
b.route = "Line 1"
b.driver = assign_driver("Fatmir")
At the end of execution of the above script, what is value of?
| b.route: | |
| b.driver.name: |
Exercises
class Hen:
"""Represents a hen"""
class Robot:
"""Represents a robot"""
def print_robot_hen(robot):
s = "name: {}, pet's name: {}\n{}'s pet's favorite food is {}."
print(s.format(robot.name, robot.pet.name, robot.name, robot.pet.fav_food))
Define a function, create_hen, which takes two strings and one integer, name, fav_food and age, creates a Hen object, assigns name to object's name attribute, fav_food to object's fav_food attribute and age to object's age attribute, and returns the object
Create a robot, robot4, and add name attribute to it, which is a string representing robot's name
Call create_hen, passing the required arguments, and assign it's return value to pet attribute of robot4
Call print_robot_hen, passing robot4 as argument
Create classes Car and Engine.
Create a car with a brand.
Write a function, build_engine(hp) that returns an Engine instance with such hp
Call build_engine, passing the required arguments, and assign it's return value to engine attribute of created car.
Create classes Family and Person.
Create a family.
Write a function, make_person(name) that returns a person with such name.
Create some people using make_person function, and add them to the created family's members list
Create classes Building and Door.
Create a building.
Write a function, create_door(material) that returns a door of such material.
Create some people using create_door function, and add them to the created building's doors list
class Laptop:
pass
class Charger:
pass
def make_charger(watts):
c = Charger()
c.watts = watts
return c
l = Laptop()
l.brand = "HP"
l.charger = make_charger(65)
At the end of execution of the above script, what is value of?
| l.brand: | |
| l.charger.watts: |