{"id":75324,"date":"2020-01-20T10:16:51","date_gmt":"2020-01-20T04:46:51","guid":{"rendered":"https:\/\/techvidvan.com\/tutorials\/?p=75324"},"modified":"2020-01-20T10:16:51","modified_gmt":"2020-01-20T04:46:51","slug":"python-functions","status":"publish","type":"post","link":"https:\/\/techvidvan.com\/tutorials\/python-functions\/","title":{"rendered":"Python Functions – Engage into the Functions of Python Programming"},"content":{"rendered":"

Python is object-oriented<\/strong> but also supports functional programming<\/strong>.<\/p>\n

In this tutorial, you will learn about Python functions<\/strong> and will learn to create<\/strong> them and call<\/strong> them.<\/p>\n

Also, you will get to understand the parameters<\/strong> of functions<\/strong> in Python, the return statement<\/strong>, anonymous functions<\/strong> in Python, and lastly, you will see what is recursion in Python<\/strong>.<\/p>\n

What are Functions in Python?<\/h3>\n

A function is a block of code<\/strong> that has a name<\/strong> and you can call<\/strong> it. Instead of writing<\/strong> something 100 times, you can create a function<\/strong> and then call it 100 times<\/strong>. You can call it anywhere<\/strong> and anytime<\/strong> in your program. This adds reusability<\/strong> and modularity<\/strong> to your code.<\/p>\n

Functions can take arguments<\/strong> and return values<\/strong>.<\/p>\n

Types of Python Functions<\/h3>\n

Functions can be of two types – built-in<\/strong> or user-defined<\/strong>.<\/p>\n

Python has many useful built-in functions like print()<\/strong> and type()<\/strong> but in this article, we will focus on user-defined functions<\/strong>.<\/p>\n

Creating Functions in Python<\/h3>\n

To define a function, we follow this syntax:<\/p>\n

Syntax:<\/strong><\/p>\n

def func(parameters):\n  code\n  return<\/pre>\n
To define a function, you use the def keyword<\/strong>. You give the function<\/strong> a name<\/strong> and it can take some parameters<\/strong> if you want. Then you specify a block of code<\/strong> that will execute when you call<\/strong> the function<\/strong>.<\/p>\n
There are no curly braces<\/strong> in Python and so you need to indent<\/strong> this code block<\/strong> otherwise it won\u2019t work<\/strong>. You can make the function return a value<\/strong>.<\/p>\n
Let\u2019s take an example for you.<\/p>\n
Code:<\/strong><\/p>\n
def add(a,b):\n  print(\"I will add two numbers\")\n  return a+b<\/pre>\n
This function prints \u201cI will two numbers\u201d and returns<\/strong> the sum<\/strong> of two numbers<\/strong>.<\/p>\n
Code:<\/strong><\/p>\n
>>> add(2,4)<\/pre>\n
Output:<\/strong><\/p>\n
I will add two numbers
\n6<\/div>\n
Calling Functions in Python<\/h3>\n
Calling <\/strong>functions is simple<\/strong>. Take two functions:<\/p>\n
Code:<\/strong><\/p>\n
def sayhi():\n  print('Hi')<\/pre>\n
Code:<\/strong><\/p>\n
def add(a,b):\n  return a+b<\/pre>\n
This is how you will call them:<\/p>\n
Code:<\/strong><\/p>\n
>>> sayhi()<\/pre>\n
Output:<\/strong><\/p>\n
Hi<\/div>\n
Code:<\/strong><\/p>\n
>>> add(2,4)<\/pre>\n
Output:<\/strong><\/p>\n
6<\/div>\n
Python Function Parameters\"python<\/a><\/h3>\n
Functions can take values<\/strong> and operate<\/strong> on them.<\/p>\n
In the above example, the add() function<\/strong> takes parameters<\/strong> a<\/strong> and b<\/strong>.<\/p>\n
Python has 3 types of parameters<\/strong> or arguments<\/strong> other than positional\/required arguments – default<\/strong>, keyword<\/strong>, arbitrary<\/strong>.<\/p>\n
1. Default Arguments<\/h4>\n
You can specify<\/strong> a default value<\/strong> for arguments<\/strong>. If the user calls the function<\/strong>, they can skip<\/strong> providing a value<\/strong> for that argument<\/strong>. The default value is used<\/strong>.<\/p>\n
Code:<\/strong><\/p>\n
def add(a, b=4):\n  return a+b<\/pre>\n
Now you can call it with one<\/strong> or two values<\/strong>.<\/p>\n
Code:<\/strong><\/p>\n
>>> add(2,4)<\/pre>\n
Output:<\/strong><\/p>\n
6<\/div>\n
Code:<\/strong><\/p>\n
>>> add(2)<\/pre>\n
Output:<\/strong><\/p>\n
6<\/div>\n
Here b is 4 by default<\/strong> so it returns 2+4, which is 6.<\/p>\n
Functions can have any number<\/strong> of default arguments<\/strong>.<\/p>\n
2. Keyword Arguments<\/h4>\n
If you pass keyword arguments<\/strong> to a function<\/strong>, you don\u2019t need to remember the order of the parameters<\/strong>.<\/p>\n
Code:<\/strong><\/p>\n
def add(a, b):\n  return a+b<\/pre>\n
Code:<\/strong><\/p>\n
>>> add(b=4,a=2)<\/pre>\n
Output:<\/strong><\/p>\n
6<\/div>\n
3. Arbitrary Arguments<\/h4>\n
If you don\u2019t know how many arguments your function will get at runtime<\/strong>, you can use the arbitrary arguments *args<\/strong> and **kwargs<\/strong>.<\/p>\n
*args<\/strong> is a variable number<\/strong> of arguments<\/strong> and **kwargs<\/strong> is a variable number<\/strong> of keyword arguments<\/strong>. You can call<\/strong> them anything<\/strong>.<\/p>\n
Code:<\/strong><\/p>\n
def add(*args,**kwargs):\n  result=0\n  for arg in args:\n    result+=arg\n  print(result)\n  for key,value in kwargs.items():\n    print(key,value)<\/pre>\n
Code:<\/strong><\/p>\n
>>> add(2,4,6,a=8,b=10)<\/pre>\n
Output:<\/strong><\/p>\n
12
\na 8
\nb 10<\/div>\n
2, 4, 6, are in *args<\/strong> and a=8 and b=10 are in **kwargs<\/strong>.<\/p>\n
Result is 12.<\/p>\n
You cannot pass positional arguments<\/strong> after keyword arguments<\/strong>.<\/p>\n
Code:<\/strong><\/p>\n
>>> add(2,4,6,a=8,7,b=10)<\/pre>\n
Output:<\/strong><\/p>\n
SyntaxError: positional argument follows keyword argument<\/div>\n
The Return Statement in Python<\/h3>\n
It is not mandatory<\/strong> for a function to return a value<\/strong> but it can. For this, you use the return keyword<\/strong>.<\/p>\n
Code:<\/strong><\/p>\n
def show_names(names):\n  return names<\/pre>\n
Code:<\/strong><\/p>\n
>>> show_names(['Jack', 'Paris', 'Nicole'])<\/pre>\n
Output:<\/strong><\/p>\n
[‘Jack’, ‘Paris’, ‘Nicole’]<\/div>\n
This function returns a list<\/strong>.<\/p>\n
Anonymous Functions in Python<\/h3>\n
If you want a function only once or it has only one line of code<\/strong>, you can avoid giving it a name<\/strong>. They are called lambda expressions<\/strong>.<\/p>\n
Code:<\/strong><\/p>\n
>>> lambda a=2,b=4:a+b\n<function <lambda> at 0x00000198A3692168><\/pre>\n
Now to call this:<\/p>\n
Code:<\/strong><\/p>\n
>>> (lambda a=2,b=4:a+b)()<\/pre>\n
Output:<\/strong><\/p>\n
6<\/div>\n
Let\u2019s try more possibilities.<\/p>\n
Code:<\/strong><\/p>\n
>>> (lambda a,b:a+b)(2,4)<\/pre>\n
Output:<\/strong><\/p>\n
6<\/div>\n
Code:<\/strong><\/p>\n
>>> add=lambda a,b:a+b\n>>> add(2,4)<\/pre>\n
Output:<\/strong><\/p>\n
6<\/div>\n
Code:<\/strong><\/p>\n
>>> (lambda :print('Hi'))()<\/pre>\n
Output:<\/strong><\/p>\n
Hi<\/div>\n
Recursion in Python<\/h3>\n
When a function calls itself<\/strong>, it is recursion<\/strong>. In other words, when a function<\/strong> body<\/strong> has calls<\/strong> to the function itself<\/strong>, it is recursion.<\/p>\n
For recursion, you should specify a base condition<\/strong> otherwise the function can execute infinitely<\/strong>.<\/p>\n
Let\u2019s take the example of calculating factorials.<\/p>\n
Code:<\/strong><\/p>\n
def factorial(num):\n  if num==1: return 1\n  return num*factorial(num-1)<\/pre>\n
Code:<\/strong><\/p>\n
>>> factorial(4)<\/pre>\n
Output:<\/strong><\/p>\n
24<\/div>\n
factorial(4) returns 4*factorial(3). factorial(3) returns 3*factorial(2). factorial(2) returns 2*factorial(1). factorial(1) returns 1.<\/p>\n
So we have 4*3*2*1. This is equal to 24. So it returns the value 24.<\/p>\n
Summary<\/h3>\n
We will explain these topics in detail in other tutorials.<\/p>\n
This was a brief introduction of TechVidvan’s Python functions<\/strong> article. We learned about functions, creating<\/strong> them, calling<\/strong> them, parameters<\/strong>, the return statement<\/strong>, lambda expressions<\/strong>, and recursion<\/strong>.<\/p>\n","protected":false},"excerpt":{"rendered":"
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