Else Statement and Loops

You can use an else statement after a for or while loop. The code in this else statement is executed if the loop completed without being terminated.

for i in range(3):
    print(i)
else:
    print('Loop completed')

0
1
2
Loop completed

The only time the else part will not be executed is if you break out of a loop:

for i in range(5):
    print(i)
    
    if i == 3:
        break
else:
    print('Loop completed')

0
1
2
3

Worked Example

A common use for this structure is if you’re searching for an object. Consider this example where we are trying to find a 'fish' in a list:

animals = ['zebra', 'cow', 'crow', 'eel']

for animal in animals:
    if animal == 'fish':
        print('We caught a fish!')
        break
else:
    print('We did not catch a fish.')

We did not catch a fish.

animals = ['human', 'bear', 'fish', 'squid', 'crab']

for animal in animals:
    if animal == 'fish':
        print('We caught a fish!')
        break
else:
    print('We did not catch a fish.')

We caught a fish!

Of course, finding a particular object in a list is quicker and simpler using:

animals = animals = ['human', 'bear', 'fish', 'squid', 'crab']

if 'fish' in animals:
    print('We caught a fish!')
else:
    print('We did not catch a fish.')

We caught a fish!

but for more complex procedures this may not be an option.