8. Basic Object-Oriented Python (127m) Flashcards
(32 cards)
What is Object Oriented Programming in Python? What is Properties and Behaviours?
Object-oriented programming (OOP) is a programming paradigm that organizes code into objects, which are instances of classes. Python is an object-oriented programming language that supports the creation and manipulation of objects.
In OOP, objects are the building blocks that encapsulate data (properties) and behavior (methods or functions) together. Let’s delve deeper into properties and behaviors:
- Properties: Properties represent the data or attributes associated with an object. They define the state of an object and store information. In Python, properties are typically represented by variables or attributes within a class. Each object of a class has its own set of property values.
For example, consider a class named “Car.” The properties of a car object might include its color, brand, and model. These properties can be defined as variables within the class:
```python
class Car:
def __init__(self, color, brand, model):
self.color = color
self.brand = brand
self.model = model
~~~
Here, color, brand, and model are properties of the car object. You can create instances of the class and assign specific values to these properties:
```python
my_car = Car(“red”, “Toyota”, “Camry”)
print(my_car.color) # Output: red
~~~
- Behaviors: Behaviors represent the actions or operations that an object can perform. They define how an object can interact with other objects or manipulate its own state. In Python, behaviors are typically implemented as methods or functions within a class.
Continuing with our “Car” example, let’s define a behavior for the car object, such as starting the engine:
```python
class Car:
def __init__(self, color, brand, model):
self.color = color
self.brand = brand
self.model = model
def start_engine(self):
print("Engine started!") ~~~
The start_engine method allows the car object to perform the action of starting the engine. You can call this method on an instance of the class:
```python
my_car = Car(“red”, “Toyota”, “Camry”)
my_car.start_engine() # Output: Engine started!
~~~
In this case, start_engine() is the behavior associated with the car object. Different objects of the same class can invoke their own behaviors while maintaining their individual property values.
Object-oriented programming provides a powerful way to model real-world concepts, allowing you to define and manipulate objects with their own properties and behaviors.
What is OOP?
Vocab:
* OOP = Object-Oriented Programming
* Object-Oriented Programming = a way of structuring your code into groups of properties and behaviors
Example Object: Car
Properties:
* 4 wheels
* 2 doors
* Make
* Model
* Year
Behaviors:
* Stop
* Go
* Turn
Python objects
Here are the Python docs about each of these objects. It’s a good habit to check out the documentation and start getting used to reading about how things work.
* List
* String
* Dictionary
* Tuple
Things I’ve interacted with today:
Dog
* Properties: 2 eyes, 2 ears, tail
* Behaviors: fetch, bark, whine, wag tail
Oven
* Properties: buttons, door, racks, light
* Behaviors: heating, timer, light on/off
What is a class and how to write it in Python?
In Python, a class is a blueprint for creating objects. It serves as a template that defines the properties (attributes) and behaviors (methods) that objects of that class will have. The class specifies the common characteristics and functionalities shared by its instances (objects).
To define a class in Python, you use the class keyword followed by the class name. Here’s a basic syntax for creating a class:
```python
class ClassName:
# class variables and methods go here
~~~
Inside the class, you can define various elements, including:
- Constructor Method: The constructor method
\_\_init\_\_()is called when an object of the class is instantiated. It is used to initialize the object’s properties. It must haveselfas the first parameter, which refers to the object itself.
```python
class ClassName:
def __init__(self, parameter1, parameter2, …):
# initialize properties here
self.property1 = parameter1
self.property2 = parameter2
~~~
- Instance Methods: Instance methods are functions defined within the class that can be invoked on objects of the class. They can access and manipulate the object’s properties using the
selfparameter.
```python
class ClassName:
def __init__(self, parameter1, parameter2, …):
self.property1 = parameter1
self.property2 = parameter2
def method1(self, parameter1, parameter2, ...):
# method code goes here ~~~
- Class Variables: Class variables are shared among all instances of the class. They are defined within the class but outside any method. They can be accessed using the class name or any instance of the class.
```python
class ClassName:
class_variable = value
def \_\_init\_\_(self, parameter1, parameter2, ...):
self.property1 = parameter1
self.property2 = parameter2 ~~~
Here’s an example that puts it all together:
```python
class Car:
wheels = 4 # class variable
def \_\_init\_\_(self, color, brand, model):
self.color = color
self.brand = brand
self.model = model
def start_engine(self):
print("Engine started!")
def drive(self, distance):
print(f"The {self.color} {self.brand} {self.model} is driving {distance} miles.") ~~~
You can create instances of the class using the class name followed by parentheses, passing the required arguments to the constructor:
```python
my_car = Car(“red”, “Toyota”, “Camry”)
~~~
You can then access the object’s properties and invoke its methods:
```python
print(my_car.color) # Output: red
my_car.start_engine() # Output: Engine started!
my_car.drive(100) # Output: The red Toyota Camry is driving 100 miles.
~~~
This is a basic overview of defining a class in Python. Classes provide a way to create reusable and organized code, allowing you to model complex systems and create objects with specific behaviors and attributes.
Explain the following code:
class Car():
pass
my_car = Car()
print(my_car)
print(type(my_car))
print(isinstance(my_car, Car))
What output will it give?
The code snippet you provided creates a class called Car and then creates an instance of that class named my_car. It then prints the object, its type, and checks whether the object is an instance of the Car class using the isinstance() function. Let’s break down the code and examine the output it will produce:
```python
class Car():
pass
~~~
In this line, a class named Car is defined using the class keyword. The pass statement acts as a placeholder, indicating that the class body is empty. This means the Car class doesn’t have any specific properties or methods defined.
```python
my_car = Car()
~~~
Here, an instance of the Car class is created using the class name followed by parentheses. The parentheses () indicate the invocation of the class constructor or initializer method, \_\_init\_\_(). Since the class body is empty, this instance won’t have any specific properties or behaviors.
```python
print(my_car)
~~~
This line prints the value of the my_car object. However, since the Car class doesn’t have any specific implementation or string representation defined, the output will be something like <\_\_main\_\_.Car object at 0x...>. The specific memory address (0x...) may vary.
```python
print(type(my_car))
~~~
This line prints the type of the my_car object using the type() function. It will output <class '\_\_main\_\_.Car'>, indicating that my_car is an object of the Car class defined in the current module (\_\_main\_\_).
```python
print(isinstance(my_car, Car))
~~~
This line checks whether my_car is an instance of the Car class using the isinstance() function. It will return True if my_car is an instance of the Car class, and False otherwise. Since my_car is indeed created using the Car class, the output will be True.
So, overall, the code will produce the following output:
<\_\_main\_\_.Car object at 0x...> <class '\_\_main\_\_.Car'> True
The specific memory address (0x...) and representation may vary, but the output confirms that my_car is an object of the Car class and is indeed an instance of the Car class.
What does print(), type(), isinstance() do in classes and how can it help me identify classes?
In Python, the print(), type(), and isinstance() functions are commonly used tools to work with classes and objects. Here’s an explanation of what each of these functions does and how they can help you identify classes and objects:
-
print(): Theprint()function is used to display output on the console. When applied to an object, it calls the object’s\_\_str\_\_()method to get a string representation of the object, which is then printed. It helps you examine the value or representation of an object, such as its properties or other relevant information. -
type(): Thetype()function is used to determine the type of an object. When passed an object as an argument, it returns the type or class of that object. It helps you identify the class to which an object belongs. -
isinstance(): Theisinstance()function is used to check whether an object is an instance of a particular class. It takes two arguments: the object you want to check and the class you want to compare it against. It returnsTrueif the object is an instance of the class, andFalseotherwise. It helps you verify the relationship between an object and a class.
These functions are often used during development and debugging to inspect objects and verify their types. They can be helpful in the following scenarios:
- Identifying the class of an object: You can use
type()to determine the class of an object. This is particularly useful if you have multiple classes and want to confirm which class an object belongs to. - Verifying inheritance or class relationships:
isinstance()can be used to check if an object is an instance of a specific class or any of its derived classes. This helps in understanding the inheritance hierarchy and confirming relationships between classes. - Debugging and troubleshooting: By printing the object using
print(), you can examine its properties, values, or other relevant information to understand its current state and aid in debugging your code.
Overall, these functions are valuable tools for inspecting and understanding classes and objects during development, allowing you to identify classes, verify relationships, and gain insights into object properties.
When creating a blueprint for an object, you use the ` ______ `keyword. Fill in the blanks.
When creating a blueprint for an object, you use the class keyword.
Explain the following code:
class Car():
wheels = 4
doors = 2
engine = True
car_one = Car()
car_two = Car()
car_two.doors = 6
Car.doors = 4
print(f'Car One: {car_one.doors}')
print(id(car_one.doors))
print(f'Car Two: {car_two.doors}')
print(id(car_two.doors))
print(f'Car Global: {Car.doors}')
print(id(Car.doors))
What output will it give and also explain ID and will ID change if following change is made to the code Car.doors = 5.
The given code defines a Car class with some class-level attributes and creates two instances of the Car class. Here’s a breakdown of the code and its output:
```python
class Car():
wheels = 4
doors = 2
engine = True
~~~
In this section, a Car class is defined with three class-level attributes: wheels, doors, and engine. These attributes define the characteristics of a car and are shared among all instances of the Car class.
```python
car_one = Car()
car_two = Car()
~~~
Two instances of the Car class, car_one and car_two, are created using the class constructor. Both instances will have the same initial attribute values inherited from the class.
```python
car_two.doors = 6
Car.doors = 4
~~~
The attribute doors of car_two is modified directly, changing its value to 6. This modification affects only the doors attribute of car_two and doesn’t change the class-level attribute or affect other instances.
The class-level attribute doors is also modified by directly accessing it via the Car class itself. The value is changed to 4, and this change affects all instances of the Car class.
```python
print(f’Car One: {car_one.doors}’)
print(id(car_one.doors))
print(f’Car Two: {car_two.doors}’)
print(id(car_two.doors))
print(f’Car Global: {Car.doors}’)
print(id(Car.doors))
~~~
The print statements in this section output the values of doors for car_one, car_two, and the class Car itself. The id() function is used to retrieve the unique identifier of the object referenced by the attribute.
Output:
Car One: 2 <id1> Car Two: 6 <id2> Car Global: 4 <id3>
Explanation of the output:
-
Car One: 2: The value ofdoorsforcar_oneis 2, which is the initial value inherited from the class. This value hasn’t been modified forcar_one. -
<id1>: The unique identifier (memory address) of the object referenced bycar_one.doors. -
Car Two: 6: The value ofdoorsforcar_twois 6, which was directly modified for this instance. -
<id2>: The unique identifier (memory address) of the object referenced bycar_two.doors. -
Car Global: 4: The value of the class-level attributedoorsafter it was modified usingCar.doors = 4. -
<id3>: The unique identifier (memory address) of the object referenced byCar.doors.
Regarding the question about the id changing if Car.doors = 5 is made:
If you change Car.doors = 5 before the print statements, the output will be:
Car One: 2 <id1> Car Two: 6 <id2> Car Global: 5 <id4>
The id of car_one.doors and car_two.doors will remain the same since their values haven’t changed. However, the id of Car.doors will change because the value of the class-level attribute has changed, resulting in a new object being created with the value 5.
What is instance attribute in Python?
In Python, an instance attribute is a variable that belongs to a specific instance of a class. It is defined within the methods of the class and is accessed using the instance of the class. Each instance of the class has its own copy of the instance attributes.
Instance attributes are used to store data that is unique to each instance of a class. They can have different values for different instances of the same class. Instance attributes define the state of an object and can be accessed and modified using the dot notation.
Here’s an example to illustrate instance attributes in Python:
```python
class Car:
def __init__(self, brand, model):
self.brand = brand # instance attribute
self.model = model # instance attribute
def display_info(self):
print(f"Brand: {self.brand}, Model: {self.model}")
car1 = Car(“Toyota”, “Camry”)
car2 = Car(“Honda”, “Civic”)
car1.display_info() # Output: Brand: Toyota, Model: Camry
car2.display_info() # Output: Brand: Honda, Model: Civic
~~~
In the example above, the brand and model variables are instance attributes of the Car class. Each instance of the Car class (car1 and car2) has its own copy of these attributes, which can be accessed using self.brand and self.model respectively.
TeamTreeHouse Notes:
* Attributes = the name in Python for the properties of an object
* Instance attributes = attributes that are created when an object is instantiated
* Method = a function inside of a class
* Dunder method = a nickname for a method that has double underscores before and after its name (Ex: __init__)
what is \_\_init\_\_ in python?
In Python, \_\_init\_\_ is a special method, also known as the constructor, that is automatically called when an object of a class is created. It is used to initialize the attributes of the object and perform any other setup or initialization tasks.
The \_\_init\_\_ method is defined within a class and takes the self parameter, which represents the instance of the class being created. It can also take additional parameters that are used to initialize the attributes of the object.
Here’s an example to illustrate the usage of \_\_init\_\_:
```python
class Car:
def __init__(self, brand, model):
self.brand = brand
self.model = model
def display_info(self):
print(f"Brand: {self.brand}, Model: {self.model}")
car1 = Car(“Toyota”, “Camry”)
car1.display_info() # Output: Brand: Toyota, Model: Camry
~~~
In the example above, the Car class has an \_\_init\_\_ method that takes brand and model as parameters. Inside the \_\_init\_\_ method, the attributes self.brand and self.model are initialized with the values passed to the constructor.
When car1 = Car("Toyota", "Camry") is executed, the \_\_init\_\_ method is automatically called with self set to car1, and the attributes brand and model are set to “Toyota” and “Camry” respectively.
The \_\_init\_\_ method allows you to set up the initial state of an object and perform any necessary initialization tasks before using the object further. It is a common practice to define the \_\_init\_\_ method in Python classes to ensure that objects are properly initialized when created.
What is \_\_init\_\_ in python?
In Python, \_\_init\_\_ is a special method, also known as the constructor, that is automatically called when an object of a class is created. It is used to initialize the attributes of the object and perform any other setup or initialization tasks.
The \_\_init\_\_ method is defined within a class and takes the self parameter, which represents the instance of the class being created. It can also take additional parameters that are used to initialize the attributes of the object.
Here’s an example to illustrate the usage of \_\_init\_\_:
```python
class Car:
def __init__(self, brand, model):
self.brand = brand
self.model = model
def display_info(self):
print(f"Brand: {self.brand}, Model: {self.model}")
car1 = Car(“Toyota”, “Camry”)
car1.display_info() # Output: Brand: Toyota, Model: Camry
~~~
In the example above, the Car class has an \_\_init\_\_ method that takes brand and model as parameters. Inside the \_\_init\_\_ method, the attributes self.brand and self.model are initialized with the values passed to the constructor.
When car1 = Car("Toyota", "Camry") is executed, the \_\_init\_\_ method is automatically called with self set to car1, and the attributes brand and model are set to “Toyota” and “Camry” respectively.
The \_\_init\_\_ method allows you to set up the initial state of an object and perform any necessary initialization tasks before using the object further. It is a common practice to define the \_\_init\_\_ method in Python classes to ensure that objects are properly initialized when created.
What is Dunder Init?
“Dunder init” is a shorthand term for the special method \_\_init\_\_ in Python. “Dunder” is derived from “double underscore,” which is represented by the character \_\_ surrounding the method name.
The \_\_init\_\_ method is a special method in Python classes that serves as the constructor. It is automatically called when an object of a class is created, allowing you to initialize the object’s attributes and perform any necessary setup or initialization tasks.
Here’s an example to demonstrate the usage of \_\_init\_\_ (dunder init):
```python
class Car:
def __init__(self, brand, model):
self.brand = brand
self.model = model
def display_info(self):
print(f"Brand: {self.brand}, Model: {self.model}")
car1 = Car(“Toyota”, “Camry”)
car1.display_info() # Output: Brand: Toyota, Model: Camry
~~~
In the example above, \_\_init\_\_ is the dunder init method of the Car class. It takes self (representing the instance of the class) as the first parameter, followed by any additional parameters (brand and model in this case).
When car1 = Car("Toyota", "Camry") is executed, the dunder init method \_\_init\_\_ is automatically called with self set to car1 and brand and model set to “Toyota” and “Camry” respectively. Inside the \_\_init\_\_ method, the attributes self.brand and self.model are initialized with these values.
Using dunder methods like \_\_init\_\_ allows you to define the behavior of your objects at specific moments or when certain operations are performed. They provide a way to customize the behavior of Python classes to suit your needs.
Explain the following codes:
One is:
~~~
class Pet():
legs: 4
ears: 2
tail: 1
def \_\_init\_\_(self, kind, breed, age):
self.kind = kind
self.breed = breed
self.age = age
pet_1 = Pet(‘cat’, ‘indian’, 2)
pet_2 = Pet(‘dog’, ‘german’, 1)
print(f’Pet 1 is a {pet_1.kind} of {pet_1.breed} breed and is {pet_1.age} years old’)
print(f’Pet 2 is a {pet_2.kind} of {pet_2.breed} breed and is {pet_2.age} years old’)
~~~
And Two is:
class Car():
wheels = 4
doors = 2
engine = True
def \_\_init\_\_(self, model, year, make='VW Group'):
self.make = make
self.model = model
self.year = year
car_one = Car('Vento', 2014)
car_two = Car('A4', 2024, 'Audii')
print(f'Car One: {car_one.doors}')
print(id(car_one.doors))
print(f'Car Two: {car_two.doors}')
print(id(car_two.doors))
print(f'Car Global: {Car.doors}')
print(id(Car.doors))
print(f'The car one is {car_one.make} {car_one.model} {car_one.year}')
print(f'The car two is {car_two.make} {car_two.model} {car_two.year}')
Sure! Let’s go through each code snippet and explain what it does.
Code Snippet One:
```python
class Pet():
legs: 4
ears: 2
tail: 1
def \_\_init\_\_(self, kind, breed, age):
self.kind = kind
self.breed = breed
self.age = age
pet_1 = Pet(‘cat’, ‘indian’, 2)
pet_2 = Pet(‘dog’, ‘german’, 1)
print(f’Pet 1 is a {pet_1.kind} of {pet_1.breed} breed and is {pet_1.age} years old’)
print(f’Pet 2 is a {pet_2.kind} of {pet_2.breed} breed and is {pet_2.age} years old’)
~~~
Explanation:
1. The code defines a class named Pet.
2. Inside the class, there are class attributes legs, ears, and tail which are set to the specified values. These attributes are shared among all instances of the class.
3. The \_\_init\_\_ method is defined as the constructor. It takes parameters kind, breed, and age, and initializes instance attributes self.kind, self.breed, and self.age with the passed values.
4. Two instances of the Pet class, pet_1 and pet_2, are created using different arguments.
5. The print statements display information about the pets, accessing their attributes using dot notation (pet_1.kind, pet_1.breed, pet_1.age, etc.).
Output:
Pet 1 is a cat of indian breed and is 2 years old Pet 2 is a dog of german breed and is 1 years old
Code Snippet Two:
```python
class Car():
wheels = 4
doors = 2
engine = True
def \_\_init\_\_(self, model, year, make='VW Group'):
self.make = make
self.model = model
self.year = year
car_one = Car(‘Vento’, 2014)
car_two = Car(‘A4’, 2024, ‘Audii’)
print(f’Car One: {car_one.doors}’)
print(id(car_one.doors))
print(f’Car Two: {car_two.doors}’)
print(id(car_two.doors))
print(f’Car Global: {Car.doors}’)
print(id(Car.doors))
print(f’The car one is {car_one.make} {car_one.model} {car_one.year}’)
print(f’The car two is {car_two.make} {car_two.model} {car_two.year}’)
~~~
Explanation:
1. The code defines a class named Car.
2. Inside the class, there are class attributes wheels, doors, and engine which are set to the specified values. These attributes are shared among all instances of the class.
3. The \_\_init\_\_ method is defined as the constructor. It takes parameters model, year, and an optional parameter make with a default value of 'VW Group'. It initializes instance attributes self.make, self.model, and self.year with the passed values.
4. Two instances of the Car class, car_one and car_two, are created using different arguments.
5. The print statements display information about the cars, accessing their attributes using dot notation (car_one.doors, car_one.make, etc.).
6. The id() function is used to display the
memory address of the doors attribute, demonstrating that it refers to the same object across instances and the class.
Output:
Car One: 2 <id1> Car Two: 2 <id1> Car Global: 2 <id1> The car one is VW Group Vento 2014 The car two is Audii A4 2024
Note: The <id1> placeholder represents the memory address of the doors attribute, which will be different each time the code is executed.
Challenge 1: Create a class called Panda. Inside your class, create two class attributes. One called species set to ‘Ailuropoda melanoleuca’ and another called food set to ‘bamboo’.
Challenge 2: Add an __init__ method to your class. It should only take the self argument. Inside the method, create an instance attribute called is_hungry and set it equal to True.
Challenge 1: Creating the Panda class with class attributes.
```python
class Panda:
species = ‘Ailuropoda melanoleuca’
food = ‘bamboo’
~~~
In the above code, we define a class called Panda. Inside the class, we create two class attributes: species set to the string 'Ailuropoda melanoleuca' and food set to the string 'bamboo'.
Challenge 2: Adding the __init__ method and instance attribute.
```python
class Panda:
species = ‘Ailuropoda melanoleuca’
food = ‘bamboo’
def \_\_init\_\_(self):
self.is_hungry = True ~~~
In the updated code, we add the \_\_init\_\_ method to the Panda class. The \_\_init\_\_ method takes only the self argument, as it is always required in a method within a class. Inside the \_\_init\_\_ method, we create an instance attribute called is_hungry and set it to True.
Now, when you create an instance of the Panda class, the is_hungry attribute will be automatically initialized to True.
Here’s an example usage:
```python
panda = Panda()
print(panda.species) # Output: Ailuropoda melanoleuca
print(panda.food) # Output: bamboo
print(panda.is_hungry) # Output: True
~~~
In the example above, we create an instance of the Panda class called panda. We can access the class attributes species and food using the instance (panda.species and panda.food) and the instance attribute is_hungry (panda.is_hungry).
Explain the following code:
class Car():
wheels = 4
doors = 2
engine = True
def \_\_init\_\_(self, model, year, make='VW Group'):
self.make = make
self.model = model
self.year = year
self.gas = 100
self.is_moving = False
def stop(self):
if self.is_moving:
print("The Car has Stopped!")
self.is_moving = False
else:
print("The Car has already Stopped!!")
def go(self, speed):
if self.use_gas():
if not self.is_moving:
print("The Car starts is Moving")
self.is_moving = True
print(f'The car is going at {speed}')
else:
print("You have run out of gas")
self.stop()
def use_gas(self):
self.gas -= 50
if self.gas <= 0:
return False
else:
return True
car_one = Car('Vento', 2014)
car_two = Car('A4', 2024, 'Audii')
car_one.stop()
car_one.go(120)
car_one.go('fast')
car_one.stop()
car_one.stop()
car_one.go(100)
The code provided defines a class Car and demonstrates its usage. Let’s go through the code and explain its functionality step by step:
```python
class Car():
wheels = 4
doors = 2
engine = True
def \_\_init\_\_(self, model, year, make='VW Group'):
self.make = make
self.model = model
self.year = year
self.gas = 100
self.is_moving = False ~~~
- The code defines a class named
Car. - Inside the class, there are class attributes
wheels,doors, andenginewhich are set to their respective values. These attributes are shared among all instances of the class. - The
\_\_init\_\_method is defined as the constructor. It takes parametersmodel,year, and an optional parametermakewith a default value of'VW Group'. - Inside the
\_\_init\_\_method, there are instance attributesself.make,self.model,self.year,self.gas, andself.is_moving. These attributes store specific data for each instance of the class.
```python
def stop(self):
if self.is_moving:
print(“The Car has Stopped!”)
self.is_moving = False
else:
print(“The Car has already Stopped!!”)
~~~
- The
stopmethod is defined within theCarclass. - It checks the
is_movingattribute of the instance to determine if the car is already moving. - If the car is moving (
self.is_movingisTrue), it prints a message indicating that the car has stopped and updatesself.is_movingtoFalse. - If the car is not moving (
self.is_movingisFalse), it prints a message indicating that the car has already stopped.
```python
def go(self, speed):
if self.use_gas():
if not self.is_moving:
print(“The Car starts is Moving”)
self.is_moving = True
print(f’The car is going at {speed}’)
else:
print(“You have run out of gas”)
self.stop()
~~~
- The
gomethod is defined within theCarclass. - It first checks if there is enough gas by calling the
use_gasmethod. - If there is enough gas (
self.use_gas()returnsTrue), it checks if the car is not already moving (self.is_movingisFalse). - If the car is not moving, it prints a message indicating that the car has started moving and updates
self.is_movingtoTrue. - It then prints a message indicating the speed at which the car is going, using the
speedparameter passed to the method. - If there is not enough gas (
self.use_gas()returnsFalse), it prints a message indicating that the car has run out of gas and calls thestopmethod to stop the car.
```python
def use_gas(self):
self.gas -= 50
if self.gas <= 0:
return False
else:
return True
~~~
- The
use_gasmethod is defined within theCarclass. - It subtracts 50 from the
self.gasattribute to simulate gas consumption. - It then checks if the gas level is below or equal to 0. If it is, it returns
Falseto indicate that there is not enough gas. - Otherwise
, if the gas level is above 0, it returns True to indicate that there is enough gas.
```python
car_one = Car(‘Vento’, 2014)
car_two = Car(‘A4’, 2024, ‘Audii’)
car_one.stop()
car_one.go(120)
car_one.go(‘fast’)
car_one.stop()
car_one.stop()
car_one.go(100)
~~~
- Two instances of the
Carclass,car_oneandcar_two, are created with different arguments passed to the constructor. - Method calls are made on the
car_oneinstance to stop the car (car_one.stop()), go at a speed of 120 (car_one.go(120)), go at a speed of ‘fast’ (car_one.go('fast')), stop the car again (car_one.stop()), stop the car again (car_one.stop()), and finally go at a speed of 100 (car_one.go(100)).
The code demonstrates the usage of class attributes, instance attributes, methods, and instance initialization. It simulates the behavior of a car object, such as starting, stopping, and consuming gas.
Challenge 1: Using your Panda class, add two arguments to your class in the __init__ method called name and age. Set the values inside of the __init__ method using self.
class Panda:
species = 'Ailuropoda melanoleuca'
food = 'bamboo'
def \_\_init\_\_(self):
self.is_hungry = True
Challenge 2:
Create a method called eat. It should only take self as an argument. Inside of the method, set the is_hungry attribute to False, since the Panda will no longer be hungry when it eats. Also, return a string that says ‘Bao Bao eats bamboo.’ where ‘Bao Bao’ is the name attribute and ‘bamboo’ is the food attribute.
Challenge 3:
Create another method called check_if_hungry that also only takes self. Inside of the method, if the is_hungry attribute is True, then call the eat method.
Certainly! Here’s the modified code that addresses all three challenges:
```python
class Panda:
species = ‘Ailuropoda melanoleuca’
food = ‘bamboo’
def \_\_init\_\_(self, name, age):
self.name = name
self.age = age
self.is_hungry = True
def eat(self):
self.is_hungry = False
return f'{self.name} eats {self.food}.'
def check_if_hungry(self):
if self.is_hungry:
self.eat()
panda = Panda(‘Bao Bao’, 5)
print(panda.check_if_hungry())
~~~
In the modified code:
Challenge 1: The \_\_init\_\_ method of the Panda class now accepts name and age as arguments and initializes the instance attributes self.name, self.age, and self.is_hungry with the respective values.
Challenge 2: The eat method sets self.is_hungry to False to indicate that the panda is no longer hungry. It returns a string using the instance attribute self.name and the class attribute self.food.
Challenge 3: The check_if_hungry method checks if the panda is hungry (self.is_hungry is True). If so, it calls the eat method to feed the panda.
The example usage prints the result of calling the check_if_hungry method on the panda instance.
Output:
Bao Bao eats bamboo.
Now, the code correctly initializes the name and age attributes, allows the panda to eat, and checks if it is hungry before feeding it.
What is class attribute and what is instance attribute in Python?
In Python, class attributes and instance attributes are two types of attributes that can be defined in a class. They serve different purposes and have different scopes and visibility within the class.
Class Attribute:
- Class attributes are attributes that are shared among all instances of a class.
- They are defined within the class body but outside of any methods.
- Class attributes have the same value for all instances of the class.
- They are accessed using the class name or through an instance of the class.
- Class attributes are typically used to define properties or characteristics that are common to all instances of the class.
Here’s an example of a class attribute:
```python
class Car:
wheels = 4 # Class attribute
car1 = Car()
car2 = Car()
print(car1.wheels) # Output: 4
print(car2.wheels) # Output: 4
print(Car.wheels) # Output: 4
~~~
In the above code, wheels is a class attribute of the Car class. It is shared by all instances of the class. It can be accessed using the class name (Car.wheels) or through an instance (car1.wheels or car2.wheels).
Instance Attribute:
- Instance attributes are attributes that belong to individual instances of a class.
- They are defined within the methods of a class, primarily in the \_\_init\_\_ method.
- Instance attributes have different values for each instance of the class.
- They are accessed using the instance name.
- Instance attributes are typically used to represent properties or characteristics that vary from instance to instance.
Here’s an example of an instance attribute:
```python
class Car:
def __init__(self, make, model):
self.make = make # Instance attribute
self.model = model # Instance attribute
car1 = Car(“Toyota”, “Camry”)
car2 = Car(“Honda”, “Civic”)
print(car1.make) # Output: Toyota
print(car1.model) # Output: Camry
print(car2.make) # Output: Honda
print(car2.model) # Output: Civic
~~~
In the above code, make and model are instance attributes of the Car class. Each instance (car1 and car2) has its own unique values for these attributes. They are accessed using the instance names (car1.make, car1.model, car2.make, car2.model).
To summarize, class attributes are shared among all instances of a class and have the same value for each instance. Instance attributes, on the other hand, belong to individual instances and have different values for each instance.
car_one = Car('Ford','Model T')
In the code above, car_one is an \_\_\_\_\_\_\_ of our Car class.
In the code car_one = Car('Ford', 'Model T'), car_one is an instance of our Car class.
Explanation:
When we create an object using the class, it is referred to as an instance of that class. In this case, Car('Ford', 'Model T') creates an instance of the Car class with the make 'Ford' and model 'Model T'. We assign this instance to the variable car_one.
Instances have their own set of attributes and can access both instance attributes and class attributes defined within the class. They can also invoke methods defined within the class.
In the given code, car_one represents a specific car object, an instance of the Car class, with its own unique attributes and behavior.
What is the difference between method, function, class attribute, instance attribute in Python?
In Python, there are several terms that describe different concepts within the language. Here’s an explanation of the differences between methods, functions, class attributes, and instance attributes:
Method:
- A method is a function that is defined within a class and is associated with an instance of that class or the class itself.
- Methods are defined within the class body and have access to the instance or class they belong to through the self parameter (for instance methods) or the class name (for class methods and static methods).
- Methods can operate on the data stored in the instance or class and can modify or retrieve instance attributes or invoke other methods.
- Example: def my_method(self, arg1, arg2): ...
Function:
- A function is a block of reusable code that performs a specific task and can be called from anywhere in the code.
- Functions can be defined outside of any class and can be used independently without any association with specific instances or classes.
- Functions typically take input arguments, perform some operations, and optionally return a result.
- Example: def my_function(arg1, arg2): ...
Class Attribute:
- A class attribute is a variable that is defined within a class and is shared among all instances of that class.
- Class attributes are defined within the class body but outside of any methods.
- They have the same value for all instances of the class and can be accessed using the class name or through instances of the class.
- Class attributes typically represent properties or characteristics that are common to all instances of the class.
- Example: attribute = value
Instance Attribute:
- An instance attribute is a variable that belongs to a specific instance of a class.
- Instance attributes are defined within the methods of a class, primarily in the \_\_init\_\_ method, and are initialized when an instance is created.
- They have different values for each instance of the class and can be accessed and modified using the instance name.
- Instance attributes typically represent properties or characteristics that vary from instance to instance.
- Example: self.attribute = value (inside \_\_init\_\_ or other instance methods)
To summarize:
- Methods are functions defined within a class that operate on instances or the class itself.
- Functions are standalone blocks of reusable code that can be called from anywhere.
- Class attributes are variables shared among all instances of a class.
- Instance attributes are variables that belong to specific instances of a class.
In the following code:
class Car:
# Class Attributes
wheels = 4
doors = 2
engine = True
# The Initializer
def \_\_init\_\_(self, model, year, make='Ford', gas=100):
# Instance Attributes
self.make = make
self.model = model
self.year = year
self.gas = gas
# instance attributes don't have
# to be passed in
self.is_moving = False
def \_\_str\_\_(self):
return f'{self.make} {self.model} {self.year}'
def use_gas(self):
self.gas -= 50
if self.gas <= 0:
return False
return True
def stop(self):
if self.is_moving:
print('The car has stopped.')
self.is_moving = False
else:
print('The car has already stopped.')
def go(self, speed):
if self.use_gas():
if not self.is_moving:
print('The car starts moving.')
self.is_moving = True
print(f'The car is going {speed}.')
else:
print("You've run out of gas!")
self.stop()
car_one = Car('Model T', 1908)
car_two = Car('Phantom', 2020, 'Rolls Royce')
print(dir(car_one))
print(car_one)
print(str(car_one))
Explain dir function and str method.
The dir function and the \_\_str\_\_ method are both related to object-oriented programming in Python and provide information about objects.
-
dir(object):
Thedirfunction is a built-in Python function that returns a sorted list of attributes and methods of the specified object. When called with an object as its argument,dirreturns a list of names that are defined in the object’s namespace.
In the given code, print(dir(car_one)) outputs a sorted list of attributes and methods for the car_one object. This includes both the attributes and methods inherited from the object class and the attributes and methods specific to the Car class.
-
\_\_str\_\_method:
The\_\_str\_\_method is a special method in Python classes that defines the string representation of an object. It is called by thestr()function and theprint()function to get a printable string representation of the object.
In the given code, the Car class defines its own \_\_str\_\_ method:
```python
def __str__(self):
return f’{self.make} {self.model} {self.year}’
~~~
This method returns a formatted string that represents the car’s make, model, and year. When print(car_one) or str(car_one) is called, it invokes the \_\_str\_\_ method of the car_one object, which returns the desired string representation.
Therefore, print(car_one) and print(str(car_one)) both output the string representation of the car_one object, which in this case would be something like: “Ford Model T 1908”.
What does iter method (dunder iter) do in Python?
The \_\_iter\_\_ method, also known as the dunder iter method, is a special method in Python classes that enables an object to be iterable. It allows an object to define its own iteration behavior when used in a for loop or when the iter() function is called on the object.
The \_\_iter\_\_ method should return an iterator object. An iterator is an object that implements the \_\_next\_\_ method, which returns the next item in the iteration. If there are no more items, the \_\_next\_\_ method should raise the StopIteration exception.
Here’s a simple example to illustrate the usage of \_\_iter\_\_:
```python
class MyIterable:
def __init__(self, data):
self.data = data
def \_\_iter\_\_(self):
# Returning an iterator object
return iter(self.data)
my_iterable = MyIterable([1, 2, 3, 4, 5])
for item in my_iterable:
print(item)
~~~
In the example, the MyIterable class defines the \_\_iter\_\_ method, which simply returns an iterator object using the iter() function and passing the self.data list as an argument. The iter() function converts the list into an iterator.
When the for loop is executed, it calls the iter() function on the my_iterable object. This, in turn, invokes the \_\_iter\_\_ method, which returns an iterator. The for loop then calls the \_\_next\_\_ method on the iterator repeatedly until it encounters the StopIteration exception.
In summary, the \_\_iter\_\_ method allows objects to be iterated over using the Python iteration protocol, enabling them to be used in for loops and other iterable contexts.
Explain the following code:
class Car:
# Class Attributes
wheels = 4
doors = 2
engine = True
# The Initializer
def \_\_init\_\_(self, model, year, make='Ford', gas=100):
# Instance Attributes
self.make = make
self.model = model
self.year = year
self.gas = gas
# instance attributes don't have
# to be passed in
self.is_moving = False
def \_\_str\_\_(self):
return f'{self.make} {self.model} {self.year}'
def use_gas(self):
self.gas -= 50
if self.gas <= 0:
return False
return True
def stop(self):
if self.is_moving:
print('The car has stopped.')
self.is_moving = False
else:
print('The car has already stopped.')
def go(self, speed):
if self.use_gas():
if not self.is_moving:
print('The car starts moving.')
self.is_moving = True
print(f'The car is going {speed}.')
else:
print("You've run out of gas!")
self.stop()
class Dealership:
def \_\_init\_\_(self):
self.cars = ["Ford Fusion", "Honda Civic", "Dodge Dakota"]
def \_\_iter\_\_(self):
yield from self.cars
car_one = Car('Model T', 1908)
my_dealership = Dealership()
for car in my_dealership:
print(car)
Explain dunder iter and also what does yield from means?
In the provided code, there are two classes: Car and Dealership. The Dealership class implements the \_\_iter\_\_ method using the yield from syntax. Let’s explain the concepts involved:
-
\_\_iter\_\_method:
The\_\_iter\_\_method is a special method in Python classes that allows an object to be an iterable. When defined in a class, it should return an iterator object. In this case, the\_\_iter\_\_method is defined in theDealershipclass. -
yield fromstatement:
Theyield fromstatement is used within the\_\_iter\_\_method to delegate the iteration to another iterable, in this case, theself.carslist. It simplifies the process of creating iterators by allowing one iterable to yield values from another iterable. Theyield fromstatement was introduced in Python 3.3 as a way to delegate to a subgenerator or another iterable.
In the given code, the Dealership class has a list of cars stored in the self.cars attribute. The \_\_iter\_\_ method uses the yield from statement to delegate the iteration to the self.cars list. This means that when the for loop iterates over an instance of the Dealership class, it will yield each car from the self.cars list.
Here’s a breakdown of the code execution:
- An instance of the
Dealershipclass,my_dealership, is created. - The
forloop iterates overmy_dealership. - Since
my_dealershiphas the\_\_iter\_\_method defined, it is considered iterable. - The
\_\_iter\_\_method is called, and it usesyield from self.carsto yield each car from theself.carslist. - The
forloop receives each car value and prints it.
In summary, the \_\_iter\_\_ method with yield from allows the Dealership class to be iterable, and the for loop in the code iterates over the cars in the dealership and prints each car’s name.
Explain the following code:
class Car:
# Class Attributes
wheels = 4
doors = 2
engine = True
# The Initializer
def \_\_init\_\_(self, model, year, make='Ford', gas=100):
# Instance Attributes
self.make = make
self.model = model
self.year = year
self.gas = gas
# instance attributes don't have
# to be passed in
self.is_moving = False
def \_\_str\_\_(self):
return f'{self.make} {self.model} {self.year}'
def use_gas(self):
self.gas -= 50
if self.gas <= 0:
return False
return True
def stop(self):
if self.is_moving:
print('The car has stopped.')
self.is_moving = False
else:
print('The car has already stopped.')
def go(self, speed):
if self.use_gas():
if not self.is_moving:
print('The car starts moving.')
self.is_moving = True
print(f'The car is going {speed}.')
else:
print("You've run out of gas!")
self.stop()
class Dealership:
def \_\_init\_\_(self):
self.cars = []
def \_\_iter\_\_(self):
yield from self.cars
def add_car(self, car):
self.cars.append(car)
car_one = Car('Model T', 1908)
car_two = Car('Fusion', 1990)
car_three = Car('Fiesta', 2000)
my_dealership = Dealership()
my_dealership.add_car(car_one)
my_dealership.add_car(car_two)
my_dealership.add_car(car_three)
for car in my_dealership:
print(car)
Also explain what will happen if:
def \_\_str\_\_(self):
return f'{self.make} {self.model} {self.year}
is removed from the above code, what will it return and why?
The provided code includes two classes: Car and Dealership. The Car class represents a car object with various attributes and methods, and the Dealership class represents a dealership that can hold multiple cars.
In the code, car_one, car_two, and car_three are instances of the Car class, and they are added to the my_dealership instance of the Dealership class using the add_car method.
The Dealership class has the \_\_iter\_\_ method implemented using yield from self.cars. This makes it iterable, allowing the for loop to iterate over the cars stored in the self.cars list.
When the for loop is executed with for car in my_dealership, it calls the \_\_iter\_\_ method on my_dealership, which uses yield from to yield each car from the self.cars list. The cars are then printed inside the for loop.
Now, let’s discuss what would happen if the \_\_str\_\_ method is removed from the Car class:
```python
def __str__(self):
return f’{self.make} {self.model} {self.year}’
~~~
The \_\_str\_\_ method is responsible for providing a string representation of the Car object. When it is removed, the default string representation provided by the object class is used. The default representation will include the class name and the memory address of the object, something like <\_\_main\_\_.Car object at 0x00000123456789>, where 0x00000123456789 is the memory address.
So, without the \_\_str\_\_ method, when the print(car) statement is executed in the for loop, it will print the default string representation of the Car object, displaying the class name and memory address.
Create the code with following condition:
- Create a class with attributes
- Definie init method
- Define str
- Create another class for library
- Define init in the new class with an empty
- Create empty list [] within the init
- Define iter in the new class
- Use yield within the iter
- define add to library
- create append to add to the empty list
- Call out above functions and add items to the list
- Use for loop to print the items in the list.
Example 1:
~~~
class Game:
console: ‘Playstation’
kind: ‘AAA Game’
def \_\_init\_\_(self, title, developer):
self.title = title
self.developer = developer
def \_\_str\_\_(self):
return f'{self.developer} {self.title}'
class Game_library:
def __init__(self):
self.games = []
def \_\_iter\_\_(self):
yield from self.games
def add_games(self, game):
self.games.append(game)
game1 = Game(‘GTA 5’, ‘Rockstar Games’)
game2 = Game(‘Sonic’, ‘Sega’)
game3 = Game(‘Hogwarts Legacy’, ‘Warner Bros.’)
game_library = Game_library()
game_library.add_games(game1)
game_library.add_games(game2)
game_library.add_games(game3)
for game in game_library:
print(game)
~~~
Example 2:
class Candy:
def \_\_init\_\_(self, name, color):
self.name = name
self.color = color
def \_\_str\_\_(self):
return f'{self.color} {self.name}'
class CandyStore:
def \_\_init\_\_(self):
self.candies = []
def \_\_iter\_\_(self):
yield from self.candies
def add_candy(self, candy):
self.candies.append(candy)
nerds = Candy('Nerds', 'Multi')
chocolate = Candy("Hersey's Bar", 'Brown')
my_store = CandyStore()
my_store.add_candy(nerds)
my_store.add_candy(chocolate)
for candy in my_store:
print(candy)
What is dunder equals? What does it do?
In Python, “dunder” is a shorthand term for “double underscore.” Dunder methods, also known as magic methods or special methods, are a set of predefined methods in Python classes that enable you to define the behavior of objects for built-in operations and syntax.
“Dunder equals” refers to the \_\_eq\_\_ method, which is a dunder method used for equality comparison. It allows objects to define their own custom equality logic when using the == operator.
The \_\_eq\_\_ method takes two parameters: self (representing the current instance) and other (representing the object being compared to). It should return True if the objects are considered equal according to the defined equality logic, and False otherwise.
Here’s an example of how to define the \_\_eq\_\_ method in a class:
```python
class MyClass:
def __init__(self, value):
self.value = value
def \_\_eq\_\_(self, other):
if isinstance(other, MyClass):
return self.value == other.value
return False ~~~
In this example, the MyClass class has an instance attribute value. The \_\_eq\_\_ method is defined to compare the value attribute of two MyClass objects. It first checks if the other object is an instance of MyClass using isinstance(other, MyClass). If it is, the method compares the value attributes of both objects. If they are equal, it returns True; otherwise, it returns False.
By defining the \_\_eq\_\_ method, you can customize the behavior of the equality comparison operator == for objects of your class.
