- A class is like a "blueprint" for creating objects. or you can say that it is a template for creating objects.
- If you define a function inside a class, it’s called a method. Methods are used by instances of a class.
class Dog:
def __init__(self, name, age):
self.name = name # Assigning the name to the instance
self.age = age # Assigning the age to the instance
def bark(self):
return f"{self.name} says woof!"
# Creating an instance of Dog
my_dog = Dog("Buddy", 3)
print(my_dog.name) # Output: Buddy
print(my_dog.age) # Output: 3
print(my_dog.bark()) # Output: Buddy says woof!-
__init__: The init method is crucial in object-oriented programming in Python. It is a special method automatically called when an object is created from a class. This method allows us to initialize an object's attributes and perform any necessary setup or initialization tasks. Without init, initialization would have to be done manually each time an object is created, leading to potential errors and less maintainable code. So the general idea is, provide all the information your object needs in init. -
self: In Python, the term “self” refers to the custom class used to access the class's members and methods, as well as to create new members. You always pass self as the first argument and you’d typically assign any other keyword arguments to the self. -
f-string : the
fin program indicates an f-string, which is a formatted string literal in Python. It allows you to include expressions inside curly braces {} directly within the string. Here, self.name is evaluated, and its value is included in the string.
- Python allows for variables to be used at the instance level or the class level.
- Those used at the instance level are referred to as instance variables.
class Demo:
def __init__(self, value):
self.instance_var = value
d1 = Demo(100)
d2 = Demo(200)
print("d1's instance variable is equal to:", d1.instance_var)
print("d2's instance variable is equal to:", d2.instance_var)- The variables used at the class level are referred to as class variables.
- Class variables are defined within the class construction, so these variables are available before any class instance is created.
- To get access to a class variable, simply access it using the class name, and then provide the variable name.
- Similarly to instance variables, class variables are shown in the class's
__dict__dictionary.
class Demo:
class_var = 'shared variable'
print(Demo.class_var)
print(Demo.__dict__)-
As a class variable is present before any instance of the class is created, it can be used to store some meta data relevant to the class, rather than to the instances. fixed information like description, configuration, or identification values; mutable information like the number of instances created (if we add a code to increment the value of a designated variable every time we create a class instance)
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A class variable is a class property that exists in just one copy, and it is stored outside any class instance.
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Because it is owned by the class itself, all class variables are shared by all instances of the class. They will therefore generally have the same value for every instance; but as the class variable is defined outside the object, it is not listed in the object's
__dict__. -
When you want to set or change a value of the class variable, you should access it via the class, but not the class instance, as you can do for reading.
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When you try to set a value for the class variable using the object (a variable referring to the object or self keyword) but not the class, you are creating an instance variable that holds the same name as the class variable.
