Functions In Python-

Python Functions-

  • – A block of instructions/statements
  • – A function consists of a block of code which is reusable and can be accessed only when it is called.
  • – It can be used for a single and relatable action. With the help of functions, a particular program can provide a better approach for the application, and it can be seen in the case of Python as well.
  • – Different programming languages follow a particular set of functions which run automatically during the execution of the program.
  • – These functions are called the main function and it needs to have a return type and arguments with respect to the standard of the language.
  • – In the case of Python, there are some built-in functions, however, python does not have some special type of functions which can be executed automatically during running a program.

Describing A Function In Python-

  • For defining a Functions in python, some rules need to be followed, which are described below:
  • – In case of python, for defining a function, it is required to start the function with a keyword ‘def’, followed by the function name, along with the parentheses.
  • – The input parameters or any kind of arguments need to be there within the parenthesis and the users can define the parameters in this as well.
  • – The function may contain some optional statements and these first statement is known as the docstring.
  • – The users can place a return statement at the end of the function for exiting from the functions.

Function Comes With Below Two Attributes-

  • 1) Function Definition
  • 2) Function Calling

1) Function Definition In Python-

  • – A set of logical statements which is used to perform a specific task.
  • – We can call the function definition by function calling mechanism.

Ex- def subtraction(a, b): # function definition c = a – b return c sub = subtraction(70, 30) # function calling print(“The subtraction is- “, sub) Output- The subtraction is- 40

Types Of Functions In Python-

1) No Arg & No Return Value

def fun():
    ----
    ---- 
fun()

2) With Arg & No Return Value

def fun(x):
    -----
    -----   
fun()

3) With Arg & With Return Value-

def fun(x):
    ----
    ----
    return 'a'
fun(10)

4) No Arg With Return Value-

def fun():
    -----
    -----
    return 'abc'
fun()

Notes- It is not recommended to call the function before its definition. ************************************

Types Of Functions On The Basis Of Argument Passed-

  • 1) Default argument function
  • 2) Required argument function
  • 3) Keyword argument function
  • 4) Variable argument function

1) Default Argument Function-

  • – Passing the default argument will always treat as optional parameter.
  • – We will not face the error if we will not pass this in any function.
  • – Default argument can only be used at last during argument passing mechanism.
  • – In case we pass the parameter then existing default argument value will be replaced by passing argument.

Ex-

def test(a, b=50): #Default argument b=50
    print(a)
    print(b)
    print("****")

test(20, 30) # b=30 will override default value. so b will be 30
test(40) #b will be 50 as we didn't passed any value for argument b. So be will be 50
test(10, "Python") # b="Python" will override default value. so b will be 'Python'

Output-
	20
	30
	****
	40
	50
	****
	10
	Python
	****

2) Required Argument Function-

  • – During function call, it is always mandatory to pass the parameter for all the argument.
  • – It is the same kind of function we have in other programming languages as well like functions in C, C++ or in Java.

Ex-

def test(a, b):  
    print(a)
    print(b)

test(7, 2)

Output-
	7
	2

3) Keyword Argument Function-

  • – We can pass the parameter using the argument name as a keyword.
  • – In the case of keyword argument function, there is no need to follow the order of the arguments during the function calling.

Ex-

def test(name, id, loc="Delhi"):
    print("name", name)
    print("id", id)
    print("address", loc)
    print("***********")

test("Python", 27)
test(27, "Python")
test(id=27, name="Rohit", loc="UP")  # Keyword name should same. Ordering doesn't matter.

Output-
	name Python
	id 27
	address Delhi
	***********
	name 27
	id Python
	address Delhi
	***********
	name Rohit
	id 27
	address UP
	***********

4) Variable Argument Function-

  • – We can use this variable type of function when we don’t know the length of parameter which will be passed during function call.
  • – This is one of the cause of not having method overloading in Python.

Ex-

def Test(*aa): #*aa - Dynamic memory allocation
    print(aa)
Test(10, 20, 'Python')
Output-
	(10, 20, 'Python') #This is a tuple.

Ex-
def f1(*args): #Argument function
    print(args) #Return tuple
f1(10,20,30)

print("***********************")

def f2(**kwargs): #Keyword argument function
    print(kwargs) # Return dictonary
f2(name='Python', rollno=101, sal=77777)

Output-
(10, 20, 30)
***********************
{'name': 'Python', 'rollno': 101, 'sal': 77777}

Notes-

– i++ and ++i are not allowed in Python.

Examples Of Some Built-In Functions Of Python-

  • The interpreter of python assistance of numerous function for executing the program, some illustrations of them are given below:
  • any(), id(), sum(), str(), print(), open(), range(), reversed(), bytes (), map(), input (), vars(), round() and so on.
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