Functions In Python

A function is a group of statements that performs a specific task and solve a specific problem. Functions help us to break our programs to smaller tasks. As our program grows larger and larger without using functions , functions make it more organized ,easy, small and manageable to be able to add and remove from it. in addition to , it avoids repetition and makes the code reusable. it help us to design or code and make it follow The principle of SOLID so make a function if you need it more than one time or in many places just call it and it will do what you need without repeating code.

1 : Function created by keyword called def

2 : Add function Name which should be lower case and not python keywords and separate name with (_)underscore to make it easy to read

3 : Add () inside them we will add parameters

Let's define small function

#function to add two numbers and return their sum
 def add(firstParr, secdParr):
  result = firstParr + secdParr
  print("The sum of " + str(firstParr) +" and "+str(secdParr) + " is "+ str(result) )
 #Taking input from user
 x = int(input("Enter Your First Number "))
 y = int(input("Enter Your Secend Number "))
 #call function add with 2 parameters x and y
 add(x, y)

Enter Your First Number 5
 Enter Your Secend Number 4
 The sum of 5 and 4 is 9
 

parameter vs argument

They are the same ("information that passed to the function to be used in operations)

But their exist a small different between them,

Parameter is exist when declare function and Argument is the value passed to the function when it called

# show difference between argument and parameter
 def difference(x):
  print(x)
 difference(x = "date")
 #here x is the parameter and "date" is the argument

output:

date

In function you can use return statement which mean you will use it again when call function in another function in the down code we make two functions functions 1: multiply which return multiply of two numbers and not print the result of them just return it 2: use_return function in it we use the return statement from multiply function rather code again or print two statement.

def multiply(num1, num2):
  return num1 * num2
 
 def use_return():
  num1 = int(input("Enter Your First Number "))
  num2 = int(input("Enter Your Secend Number "))
  result = multiply(num1,num2)
  print("The Result Of Multiply " +str(num1)+" and " +str(num2)+ " is " + str(result))
 use_return()

Enter Your First Number 6
 Enter Your Secend Number 7
 The Result Of Multiply 6 and 7 is 42

Built-in functions

Functions that are built into Python which mean you can use it just by import as sum, sqrt, ceil ,floor ,round and pow

User-defined functions

Functions defined by the users themselves. this is as any function you type and call in python

def import_biltIn_inUserDefiend_function():
  listA = [1, 2, 3, 4, 5, 7 ,27 , 25]
  print(sum(listA))
 call_biltIn_inUserDefiend_function()