Python – Functions

Hello Technotizers, this article will give you detailed information on Python Functions. Function is a block of code that is designed to perform a specific task. It runs only when it is called in the code. A function can be given some data known as parameters which is used in the function. It can also return some result.

·         Creating a Function:

In Python, a function is created or defined using the def keyword.

def my_func():                     
    print("Hello, I'm a function!")

my_func is the name of the function.

 

·         Calling a Function:

To call a function, the name of the function is written followed by parenthesis.

def my_func():                     
    print("Hello, I'm a function!")
my_func()                          

The output is obtained as:

Hello, I'm a function!    

The task written in the function of printing a line is done when the function is called in the code. The function can be called multiple times and it will give the same output multiple times.

 

·         Arguments:

Information passed inside a function are called arguments. There can be multiple number of arguments inside a function, separated by a comma. Arguments are written inside parenthesis after the function name.

def my_name(name):            
    print("My name is",name)  
my_name("Harsh")              
my_name("Simran")             

The output is obtained as:

My name is Harsh    
My name is Simran   

In the above example, the function is created using one argument ‘name’. When the function is called the name is passed in parenthesis with the function name. This name is then used in the function to print the entire sentence.

 

Arguments or Parameters?

These both are used for the same thing, information passed in a function. But there is a major difference from the function’s perspective. A parameter is the variable name inside the parentheses in the function definition. An argument is the value that is sent to the function when it is called in place of the parameter.

 

Number of Arguments

The number of arguments passed while defining the function and the number of arguments passed while calling the function should be the same. Example: If a function is defined with 2 arguments then it should be called with 2 arguments only. Using 1 or 3 arguments will generate an error.

def my_name(fname,lname):            
    print("My name is",fname,lname)  
my_name("Harsh")                     

The output is obtained as:

TypeError: my_name() missing 1 required positional argument: 'lname'.

The error shows that the function is missing one argument.

 

Arbitary Arguments

When the number of arguments to be passed is not known, we need to add a * before the parameter name in the function definition. With this the function will receive a tuple of arguments and access the items accordingly.

def my_name(*names):                
    print("My name is",names[2])    
my_name("Simran","Tanuja","Harsh")  

The output is obtained as:

My name is Harsh

 Arbitrary Arguments are often shortened to *args in Python documentations.

Keyword Arguments

We can also pass the arguments in key =  value pairs. In this way, the order of arguments does not matter.

def my_name(name2,name3,name1):                           
    print("My name is",name3)                             
my_name(name1 = "Simran",name2 = "Tanuja",name3 = "Harsh")

The output is obtained as:

My name is Harsh

Keyword Arguments are often shortened to kwargs in Python documentations.

Arbitary Keyword Arguments

When the number of keyword arguments to be passed is not known, we need to add ** before the parameter name in the function definition. With this the function will receive a dictionary of arguments and access the items accordingly with the help of keys.

def my_name(**name):                     
    print("My name is",name2)            
my_name(name1 = "Simran",name2 = "Harsh")

The output is obtained as:

My name is Harsh

Arbitrary Keyword Arguments are often shortened to **kwargs in Python documentations.

 

·         Default Parameters:

Default parameter is used when no argument value is passed to the function. Default parameter is assigned while defining the function, by writing the default parameter value in front of the parameter name.

def my_name(name = "Harsh"):
    print("My name is",name)
my_name("Simran")           
my_name()                   
my_name("Tanuja")           

The output is obtained as:

My name is Simran    
My name is Harsh     
My name is Tanuja    

In the above example, the default parameter value is “Harsh”, so when the function was called without an argument, it used the default parameter value to print the statement.

·         Passing any data type as Argument:

Python allows any data type to be passed as an argument. The data type doesn’t lose its identity while being used as an argument.

Example: Passing list as an argument.

def my_name(names):                
    for i in names:                
        print("My name is",i)      
names = ["Simran","Harsh","Tanuja"]
my_name(names)                     

The output is obtained as:

My name is Simran    
My name is Harsh     
My name is Tanuja    

 

·         Return Values:

To return some information as result, use the return keyword.

def my_func(number):       
    return 6*number        
print("2*6 is:",my_func(2))
print("3*6 is:",my_func(3))
print("5*6 is:",my_func(5))

The output is obtained as:

2*6 is: 12    
3*6 is: 18    
5*6 is: 30    

·         Pass Statement:

function definitions cannot be empty, but if you for some reason have a function definition with no content, put in the pass statement to avoid getting an error.

def my_func():    
    pass          

This code will show no output as pass keyword is used in the function.

 

·         Recursion:

Recursion is a method where a function calls its self. In lay man’s language, recursion can be considered as nested functions. Recursion is a very common mathematical and programming concept. It’s benefit is that we can loop through data to reach a result. The programmer should be very careful with recursion as it can be quite common to fall into writing a function which never terminates, or one that uses excess amounts of memory or processor power. However, when written aptly recursion can be a very efficient and mathematically-elegant approach to programming.

def recursion(number):                       
    if number>0:                             
        result = number + recursion(number-1)
        print(result)                        
    else:                                    
        result = 0                           
    return result                            
print("Recursion results:")                  
recursion(6)                                 

The output is obtained as:

Recursion results:
1                 
3                 
6                 
10                
15                
21                

In this recursion, the argument value is added with the next recursion result which continues in loop until the number becomes 0.

 

With this we come to an end of this article. Hope it was helpful. Do provide your feedback and ideas through comments, it would be highly appreciated. See you soon!

Keep coding and exploring new techs!!