Functions in a programming language are a piece of code that focus on reusability and abstraction in the application. These can be called any number of times in a program, within or from another file. This is a fundamental concept adopted in every programming language and is very helpful while practicing Machine Learning too. 

There are instances where we want to perform custom preprocessing steps aligned to a specific use case and it can be a mess if that code overshadows other essential tasks involved in data science. The isolation of this code and calling it once for performing a chunk of operations is a common practice that promotes clean coding. 

While creating functions, there are some inputs that it may take from the user to process the instructions enclosed within that function. These inputs are usually confused between two terminologies: Arguments and Parameters. Let’s look at the difference between them and find out which one to use at which place. 

Parameters

These are the variables that are used within the function and are declared in the function header. The data type specification depends on the programming language used in the function definition. These variables help in the complete execution of the function. These can also be coined as local variables as they are not accessible outside the function. The values contained by these parameters can only be accessed from function return statements or if the scope of these parameters is made global. 

Arguments

The functions defined can be called anywhere within the file or in another file in the directory depending upon the use case. Arguments are the variables that are passed to the function for execution. It is different from parameters as arguments are the actual values that are passed to the function header.

The argument values are assigned to the parameters of the function and therefore the function can process these parameters for the final output. The arguments are accessible throughout the program depending upon the scope of the variable assigned. These can be taken from the user end or can be predefined variables. 

Example For Better Understanding

The argument and parameter may seem interchangeable but they have different meanings at different places. Consider an example where we want to calculate the area of a rectangle. We are aware of the fact that the formula for the perimeter of the rectangle takes in the length and breadth of the rectangle. 

Here is how the function will look like in Python programming: 

def recPerimeter(length, breadth):

perimeter = 2*(length + breadth)

return perimeter

length_arg, breadth_arg = list(map(int, input().split()))

perimeter = recPerimeter(length_arg, breadth_arg) 

print(perimeter)

In Java, the same function would take the form of:

import java.util.Scanner;

public class Perimeter {

    public static int recPerimeter(int length, int breadth){

        int perimeter = 2 *(length + breadth);

        return perimeter;

    }

public static void main(String[] args) {

Scanner scn = new Scanner(System.in);

int length_arg = scn.nextInt();

int breadth_arg = scn.nextInt();

int perimeter_output = recPerimeter(length_arg, breadth_arg);

System.out.println(perimeter_output);

    }

}

According to the definition, the length and breadth in the function headers defined in Python or Java are the parameters, and length_arg, breadth_arg in the program are the arguments. This also proves that arguments and parameters are not language-specific and rather a notion used for the function definitions.

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Formal vs Actual Parameters

While discovering about arguments and parameters, you will come across another set of notions, i.e, formal and informal parameters. The major confusion here could be that they are subparts of parameters but they are not. The formal parameters here refer to the parameters in the functions and actual parameters refer to the arguments we pass while making a function call. 

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Conclusion

Arguments and Parameters are used in any type of programming language. These terms can confuse when referring to any resource material and a clear understanding of these is recommended. The function inputs are the most common application of these notations.

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