Lesson 03-10: The break Keyword¶

What does break do?¶

On occasion, there comes a time when you want to stop your loop right away. That’s what the break keyword does. Take the following as an example:

x = 7

​

while True:

    print(x)

    if x < 3:

        break

    x = x - 1

print("end")

​

7
6
5
4
3
2
end

(0310_ex_1)

This also works for for loops as well:

for x in range(7,0,-1):

    print(x)

    if x < 3:

        break

print("end")

​

7
6
5
4
3
2
end

(0310_ex_2)

The break keyword only quits out of the “innermost” loop. This means that if you have a loop inside of a loop (also covered later), using break will only quit out of the most recently-used loop.

When to use break?¶

break is not a keyword you should be using often in your programs. In general, you want to follow the following guidelines when you are thinking about using break:

• Use break to exit a for loop early - because there is no other way to do this.

  • This is nice because it allows us to provide two ways for a for loop to end - either it loops through everything, or it breaks due to some condition.

• In general, you should avoid using break in a while loop, because it is an indicator that you could just write a better condition for the loop.

  • Take the first example above as an example of BAD break usage. Instead of using a conditional to break out of the loop, you could’ve rewritten line 3 to while x >= 3:. This makes it easier to read and understand the purpose of the loop, and it eliminates the need of the break keyword.