Python Constructor

• It is used to initialize the values of the instance attributes of the class
• In Python the concept of constructor overloading/ multiple constructors is not present but similar functionality can be implemented by using class methods
• The cls() method call the constructor of the class which will create a new instance of the class
• The __init__ method can not have a return value (It was cause an Error)

class Animal:
    def __init__(self, species, color, name) -> None:
        self.species = species
        self.color = color
        self.name = name
 
    @classmethod
    def create_animal(cls, input_string):
        species, color, name = input_string.split("-")
        return cls(species, color, name)
 
if __name__ == '__main__':
    a1 = Animal("Cat", "White", "Cloud")
    print(a1.name)
 
    a2 = Animal.create_animal("Dog-Black-Spark")
    print(a2.name)

_new_ Attribute

• The __new__ attribute is used to create a instance of a class
• When we create a new instance of a class the __new__ method is called first followed by __init__ where the instance attributes are initialized
• It is very uncommon use case where we need to overwrite the default implementation of this method (It can be modified to implement Singleton concept)

Python: new magic method explained - Lintel Technologies Blog