Python User define Function,How to create function in python program

Python User Defined Function — How to Create Functions in Python

User-defined functions allow us to divide program logic into small reusable blocks. This improves code readability, reduces repetition, and follows the procedural pattern of Python.

Syntax of a Function

def functionname():
    statements
    ...
functionname()

Example — Addition & Subtraction Using Functions

def addition():
    a = int(input("enter first number"))
    b = int(input("enter second number"))
    print(a + b)

def substraction():
    a = int(input("enter first number"))
    b = int(input("enter second number"))
    print(a - b)

addition()
substraction()

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Example — Simple Interest Program Using Function

def calculatesi():
    p = float(input("enter value for amount"))
    r = float(input("enter value for rate"))
    t = float(input("enter value for time"))
    si = (p*r*t)/100
    print("result is ", si)

calculatesi()

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Parameterized Function Example

def addition(x, y):
    print(x + y)

def substraction():
    x = int(input("Enter First Number"))
    y = int(input("Enter Second Number"))
    print(x - y)

addition(
    int(input("Enter first number")),
    int(input("Enter Second number"))
)
substraction()

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Complete Function Based Calculator (6 Functions)

def acceptInput():
    global a, b
    a = int(input("Enter first number"))
    b = int(input("Enter second number"))

def add():
    print(a + b)

def sub():
    print(a - b)

def multi():
    print(a * b)

def division():
    print(a / b)

def executeFunction():
    while True:
        ch = input("Press + for addition \n - for Subtraction \n * for multiplication \n / for division\n")
        if ch == '+':
            acceptInput()
            add()
        elif ch == '-':
            acceptInput()
            sub()
        elif ch == '*':
            acceptInput()
            multi()
        elif ch == '/':
            acceptInput()
            division()
        else:
            break

executeFunction()

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Same Program Using Parameterized Functions

def add(a, b):
    print(a + b)

def sub(a, b):
    print(a - b)

def multi(a, b):
    print(a * b)

def division(a, b):
    print(a / b)

def executeFunction():
    while True:
        ch = input("Press +, -, *, /\n")
        if ch == '+':
            add(int(input("Num1")), int(input("Num2")))
        elif ch == '-':
            sub(int(input("Num1")), int(input("Num2")))
        elif ch == '*':
            multi(int(input("Num1")), int(input("Num2")))
        elif ch == '/':
            division(int(input("Num1")), int(input("Num2")))
        else:
            break

executeFunction()

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Example — Using Function From Separate File

File 1: Ope.py

def Add():
    a=100
    b=200
    print(a+b)

def Sub():
    a=100
    b=20
    return a - b

def Multiplication(a,b):
    print(a*b)

def Division(a,b):
    return a/b

File 2: Access File

import Ope

Ope.Add()
x = Ope.Sub()
print(x)

Ope.Multiplication(100,2)
y = Ope.Division(10,2)
print(y)

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Types of Functions in Python

1) Default / Without Parameter Function

• Input is taken inside the function
• Can be with return type or without return type

Example — With Return Type

def calculatesi():
    p = float(input("enter amount"))
    r = float(input("enter rate"))
    t = float(input("enter time"))
    return (p*r*t)/100

res = calculatesi()
print(res)

Example — Without Return Type

def addition():
    x = 100
    y = 200
    print("result is ", (x+y))

addition()

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Assignment for Default Functions

• Reverse a five-digit number using no-return function
• Add complex numbers using return function
• Create salary calculator (no return)
• Calculate compound interest (no return)

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2) Parameterized Functions

2.1 Required Arguments

def addition(x, y):
    print(x + y)

addition(10, 2)

2.2 Keyword Arguments

def addition(x, y):
    print(x / y)

addition(x=10, y=20)
addition(y=100, x=20)

2.3 Default Arguments

def addition(x=1000, y=20):
    print(x / y)

addition()
addition(400)
addition(400, 40)
addition(x=10, y=2)

2.4 Variable-Length Arguments (*args)

def addition(*x):
    for val in x:
        print("result is ", val)

addition(100,4,23,34,45,5,67)

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Lambda Function

sum = lambda x, y: x + y
print(sum(10, 20))

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Q) Find Max Using Variable Length Arguments

def calcMax(*x):
    m = 0
    for d in x:
        if d > m:
            m = d
    print(m)

calcMax(10,23,67,89,11,45)

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Salary Calculator Using User Defined Function

def SalaryCal():
    name = input("Enter name")
    basic = float(input("Enter basic salary"))
    ta = float(input("Enter ta"))
    da = float(input("Enter da"))
    comm = float(input("Enter comm"))
    pf = float(input("Enter pf"))
    hra = float(input("Enter HRA"))
    lv = float(input("Enter leave days"))

    ctc = basic + ta + da + comm + hra + pf
    print("CTC of employee is ", ctc)

    tsal = basic + ta + da + comm + hra
    lvded = (tsal/30)*lv
    gsal = tsal - lvded - pf

    print("Gross Salary is ", gsal)

    f = open("salaryslip.doc","a")
    f.write("\n--------------------")
    f.write("\n Name: "+name)
    f.write("\n Gross Salary: "+str(gsal))
    f.write("\n Leave Deduction: "+str(lvded))
    f.write("\n--------------------")
    f.close()

Execution File

import SalaryCalc

num = int(input("Enter number of employees"))
for i in range(1, num+1):
    SalaryCalc.SalaryCal()

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Assignments for Parameterized Functions

• Create mark-sheet program using dictionary
• ATM program using parameterized functions