Python else after for/while loop explained with Example
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.
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.
But, how does it work?
In Python, if you are using else statement after the loop…
The else-block will not be executed if the break statement is executed inside the loop.
This is really a tricky and exceptional concept. There are many questions asked in job interviews based on this concept.
As a part of this tutorial, you will learn using else-statement after for and while loop in Python.
Let’s take some examples.
Example: Python for else
The syntax is simple. Write else-block just after for loop.
for i in range(0,5):
print(i)
else:
print("inside else")
What is the output of this program?
Output:
0 1 2 3 4 inside else
Here else-statement is getting executed as there is no break statement inside the for-loop.
We are using range() method to iterate over for-loop.
Now, let’s add break statement inside for loop.
for i in range(0,5):
if i==3:
break;
print(i)
else:
print("inside else")
Execute the program and print the output.
Output:
0
1
2
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.
Now consider while loop.
Example: Python while else
You can also use else statement with while loop.
i=0
while i<5:
print(i)
i=i+1
else:
print("inside else")
What is the output of this program?
Output:
0 1 2 3 4 inside else
The else-block is executed as there is no break statement inside the while loop.
Now we are adding break statement inside the while loop.
i=0
while i<5:
if i==3:
break
print(i)
i=i+1
else:
print("inside else")
Run this program again and see the output.
Output:
0 1 2
As break statement has occurred inside the while-loop, else-block is not executed.
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.
Note: 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.
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Any doubt? Write in the comment.
