6.10. Ending a Loop With break

Python, like most programming languages, provides a way to stop a loop before it would normally finish. The break keyword immediately stops the execution of the loop. Program flow then continues with the next line of code below the loop.

Example

for iteration in range(42):
   print('This is iteration number:', iteration+1).

   if iteration > 4:
      break

print("The loop is done!")

Console Output

This is iteration number: 1
This is iteration number: 2
This is iteration number: 3
This is iteration number: 4
This is iteration number: 5
This is iteration number: 6
The loop is done!

1. Line 2 repeats 6 times with values of iteration from 0 to 5.

2. The sixth time through the loop, iteration is 5 and the condition in line 4 (iteration > 4) evaluates to True for the first time.

3. As a result, the program flow reaches the break statement. The loop immediately stops, even though range(42) would normally keep the loop going.

4. Control moves to the first line of code after the loop.

Why would we need to use break? After all, we tell Python how many times the loop should repeat in the for statement.

In some cases, you may want to provide a second ending condition. For example, let’s say you need to search through 100,000 items, and you find the one you want after 5 iterations. In this case, there is no need to wait for the loop to finish on its own. Adding a break statement will speed up your program, especially if you need to use that large range multiple times.

The break statement can also be used within a while loop.

Note

There is another command that interrupts a single iteration of a loop but does not end the loop completely. This is the continue statement.

However, continue is rarely used, and we will not discuss it in detail here. If you are curious, you can find more information at Tutorials Point.