Well we convered topics on variables now we are moving to the bigger topics like methods.
Before we go into those intense topics assume that you want to keep track of how many employees are there in the class ( or which refers to the organisation). For that we can create an class variable num_of_emps and intialise then to 0 and within the init method ( which is called whenever an object is created we can increment the Employee.num_of_emps by one [ The reason being that we are not using self here is that there are no use cases where we need to set the count in the instance variable to override. The class variable will give the constant idea.
Now let us look into Regular Methods, Class methods and Static Methods
The Regular Methods in the class automatically takes the instance as the first variable ( which is self by conventions). The idea of a Class method is that instead of an instance it will automatically take a class as a frist argument. To convert a regular method to a class method it is easy to add a decorator on top of the function definition. “@classmethod”. Check the code snippet below to see how a class method is created. Although we know that the first argument is class we cannot use the term so we renamed it to cls ( which was also possible in the earlier condition but we just followed the conventions as we always do 🙃 )
They say that we can use class methods as alternative constructors- by which they mean that we can use the class methods to use to provide multiple ways to create objects.
For example, where the employee info in the form of string separated by hyphens. So before creating the object they have to parse the string. Is there anyway to pass the string as such to create instances.
Check the example in the colab. The realtime example of the same use case that we encounter is with the datetime module. Where there are different ways to create the datetime ( means different ways of input and for each cases there are different class methods
Now we can look into the Static Methods most of the time people will get confused with static methods and class methods. But the case is in static method there is no argument passed automatically, neither the instance nor the class.
Assume there are some functions that make sense to the class but not necessarily related to the instance or the class variables then we can make it as a static method.
For example, consider you want to pass a data and check whether it is a workday or not. So here in this example it does not deal with any of our class variables or instance variables. Hence we can make it as a static method. Check the colab for the example