Functions in Python 2

Functions in Python

Python Function is a piece of code or any logic that performs the specific operation. We already saw some methods until now, and you may not notice them. For instance, print(), factorial(), round(), etc., are few of the built-in functions in Python programming language.

Let us see the definition, declaration, syntax, and example of using functions in Python. There are two types of functions in the Python Programming language:

  • We don’t have to bother about the logic inside the Library or built in functions in Python Programming Language. In our previous articles, We used many library methods such as print(), factorial(), round() etc.
  • User Defined: Instead of relying on built-in, Python programming language allows us to create our own called as user defined functions. For example, if we want to implement some mathematical calculations, then put them in separate methods with the correct name. Then we can call that method multiple times.

Advantages of functions in Python

  1. It helps to divide the large programs into small groups so that we can read the code, and debug the program faster and better.
  2. Python Functions stop us from writing the same logic various times. We can bind the logic in one def and then call the same over and over.
  3. Many persons can work on the same program by assigning different methods to each of them.
  4. It encourages us to call the same method with different inputs over multiple times.

Python Define Functions Syntax

The syntax to define the Functions in Python Programming is

def FName (Parameters):
        Local Variable Declaration
        Programming Logic
        Executable Statement 1
        ……
        return
  • def: Keyword def is the introduction to the definition. Remember, the Python def keyword must immediately follow by the Name to define it.
  • FName: It can be any name you wish to give other than the system reserved keywords.
  • Parameters: Every python function accepts 0 or more parameters. It completely depends upon the user requirements.
  • Local Variable Declaration: Sometimes, we may need some temporary variable only for that particular method, then we can declare the local scope variables inside it. It is not compulsory, entirely depends upon user requirements. Remember, these variables are available to this particular method only, and we can’t access them outside.
  • Logic: Any mathematical or any code or calculations you need to implement in this particular func.
  • Executable Statement: Any print statements to print some data from this particular def.
  • return: This keyword is required to return something from the method. For example, returning the sum of two integers, etc.

User Defined Functions in Python implementation

To implement the user defined functions in the Python program, we have to follow a few rules, such as:

Python Function Declaration

It informs about the def name and number of arguments.

def Name (Parameters):

For example,

def Add(a, b):

How to call a Function?

Nothing, but calling the original Python function with a valid number of arguments. For example, Add (2, 3). And remember, User defined function name should exactly match with the method calling.

Function Definition

The Python function definition is the place where we are going to put all the logic, calculations, etc. Please don’t forget the return statement inside the method body, otherwise the program not return anything. While calling it, always pass the required arguments for the function block. For example,

def Adding(a, b):
    Sum = a + b
    return Sum
print("After Calling:", Adding(3, 4))
After Calling: 7
>>> Adding(8, 9)
17

Python Function to find Sum and Average of 3 Numbers

In this Python functions program, the user asked to enter three numbers. Then by calling the method, we calculate the Sum and Average of that three numbers.

def sumAndAverage(x, y, z):
    Sum = x + y + z
    Average = Sum/3
    print("\n %d is the Total Sum of three Numbers." %Sum)
    print("\n %d is the Average of three Numbers.\n" %Average)
    
# Allows User to enter three values
a = int(input("\nPlease Enter the First Value. a =  "))
b = int(input("\nPlease Enter the Second Value. b =  "))
c = int(input("\nPlease Enter the Third Value. c =  "))

# Calling the Func
sumAndAverage(a, b, c)
sumAndAverage(10, 20, 30)
Functions in Python 2

It is called a function declaration. If you forget this func declaration, then it throws an error.

def sumAndAverage(x, y, z):

The below statements ask the user to enter 3 numbers and store the user input values in a, b, c variables

a = int(input("\nPlease Enter the First Value. a =  "))
b = int(input("\nPlease Enter the Second Value. b =  "))
c = int(input("\nPlease Enter the Third Value. c =  "))

In the next line, we are calling the Python function multiple times. First, with user-specified values, and then static 10, 20, 30.

sumAndAverage(a, b, c)
sumAndAverage(10, 20, 30)

When it reaches this method, it traverses to check for the sumAndAverage(). If it fails to identify the func name, then it throws an error.

Within the definition,

def sumAndAverage(x, y, z):
    Sum = x + y + z
    Average = Sum/3

We declared 2 local variables, Sum and Average. In the next line, we calculated the sum and average of three numbers using Assignment Operators. Please refer to print(), factorial(), and round()

Sum = x + y + z
Sum = 10 + 20 + 30 = 60

Average = Sum / 3
Average = 60 / 3 = 20

Prints the sum and average to the output.

 print("\n %d is the Total Sum of three Numbers." %Sum)
 print("\n %d is the Average of three Numbers.\n" %Average)

In the next line, We called Average() one more time, this time, we passed local variables as method arguments. We called 2 times because it helps you to understand that, we can call the func n number of times.

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