{"id":5960,"date":"2019-10-01T09:36:56","date_gmt":"2019-10-01T04:06:56","guid":{"rendered":"https:\/\/www.csestack.org\/?p=5960"},"modified":"2019-10-01T09:39:48","modified_gmt":"2019-10-01T04:09:48","slug":"python-for-while-loop-else","status":"publish","type":"post","link":"https:\/\/www.csestack.org\/python-for-while-loop-else\/","title":{"rendered":"Python else after for\/while loop explained with Example"},"content":{"rendered":"

For most of the programming languages like C\/C++, Java…, else-statement is coupled with if-statement. The else-statement can be used only with the if-statement.<\/p>\n

This is not the case with Python. As usual, you are free to use else-statement with if-statement. You can also use else-statement after for or while loop.<\/p>\n

But, how does it work?<\/strong><\/p>\n

In Python, if you are using else statement after the loop…<\/p>\n

The else-block will not be executed if the break statement is executed inside the loop<\/strong>.<\/p>\n

This is really a tricky and exceptional concept. There are many questions asked in job interviews based on this concept.<\/p>\n

As a part of this tutorial, you will learn using else-statement after for and while loop in Python.<\/p>\n

Let’s take some examples.<\/p>\n

Example: Python for else<\/h4>\n

The syntax is simple. Write else-block just after for loop.<\/p>\n

[python]
\nfor i in range(0,5):
\n print(i)<\/p>\n

else:
\n print("inside else")
\n[\/python]<\/p>\n

What is the output of this program?<\/p>\n

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

0\r\n1\r\n2\r\n3\r\n4\r\ninside else<\/pre>\n
Here else-statement is getting executed as there is no break statement inside the for-loop.<\/p>\n
We are using range() method to iterate over for-loop<\/a>.<\/p>\n
Now, let’s add break statement inside for loop.<\/p>\n
[python]
\nfor i in range(0,5):
\n    if i==3:
\n        break;
\n    print(i)<\/p>\n
else:
\n    print("inside else")
\n[\/python]<\/p>\n
Execute the program and print the output.<\/p>\n
Output:<\/strong><\/p>\n
0
\n1
\n2<\/p>\n
When i==3 inside for loop, the break statement will be executed. Control will come out of the for-loop and will not execute the else-block.<\/p>\n
Now consider while loop.<\/p>\n
Example: Python while else<\/h4>\n
You can also use else statement with while loop.<\/p>\n
[python]
\ni=0
\nwhile i<5:
\n    print(i)
\n    i=i+1<\/p>\n
else:
\n    print("inside else")
\n[\/python]<\/p>\n
What is the output of this program?<\/p>\n
Output:<\/strong><\/p>\n
0\r\n1\r\n2\r\n3\r\n4\r\ninside else<\/pre>\n
The else-block is executed as there is no break statement inside the while loop.<\/p>\n
Now we are adding break statement inside the while loop.<\/p>\n
[python]i=0
\nwhile i<5:
\n    if i==3:
\n        break
\n    print(i)
\n    i=i+1<\/p>\n
else:
\n    print("inside else")
\n[\/python]<\/p>\n
Run this program again and see the output.<\/p>\n
Output:<\/strong><\/p>\n
0\r\n1\r\n2<\/pre>\n
As break statement has occurred inside the while-loop, else-block is not executed.<\/p>\n
This is a little confusing for many of us. Just to remember- when there is a break, there is no else. When there is no break, there is else.<\/p>\n
Note:<\/strong> Python for else and Python while else statements work same in Python 2 and Python 3. You can try running this program in different Python versions.<\/p>\n
Related tutorials:<\/strong><\/p>\n