break and continue in Python (15/100 Days of Python)

Day 15 of the “100 Days of Python” blog post series covering how to stop a loop or skip an iteration

Breaking Out of Loops: The break Statement

In Python, the break statement is used to exit or break out of a loop early, before the loop has finished iterating through all of its items. This can be useful when you have a certain condition that you want to check for, and if that condition is met, you want to stop the loop and move on to the next section of your code. It can be used with a for loop:

for i in range(10):
    if i == 5:
        break
    print(i)

In this code, the for loop will iterate through the numbers 0 through 9. However, when the value of i is 5, the if statement will evaluate to True, and the break statement will be executed. This will cause the loop to exit, and the code will continue running after the loop. So the output of this code will be 0,1,2,3,4.

You can also use the break statement in a while loop in a similar way:

while True:
    n = input('Enter a number or q to quit: ')
    if n == 'q':
        break
    square = int(n) ** 2
    print('Square:', square)

In this code, the while loop will run indefinitely, prompting the user to enter a number. However, if the user enters the letter 'q', the if statement will evaluate to True, and the break statement will be executed. This will cause the loop to exit, and the code will stop running.

It’s important to note that the break statement only exits the innermost loop that it is in. If you have nested loops, you will need to use the break statement multiple times to exit all of the loops.

Skipping an iteration: The continue Statement

In addition to break statement, Python also has continue statement which is used to continue to the next iteration of the loop without executing the rest of the code in the current iteration. This can be useful when you have a certain condition that you want to check for, and if that condition is met, you want to skip the current iteration of the loop without stopping the loop entirely:

for i in range(10):
    if i % 2 == 0:
        continue
    print(i)

In this code, the for loop will iterate through the numbers 0 through 9. However, when the value of i is even, the if statement will evaluate to True, and the continue statement will be executed. This will cause the loop to skip the current iteration and move on to the next iteration, and so the output of this code will be 1,3,5,7,9.

You can also use the continue statement in a while loop in a similar way:

while True:
    n = input('Enter a number: ')
    if n.isalpha():
        continue
    square = int(n) ** 2
    print('Square:', square)

In this code, the while loop will run indefinitely, prompting the user to enter a number. However, if the user enters a non-numeric value, the if statement will evaluate to True, and the continue statement will be executed. This will cause the loop to skip the current iteration and prompt the user for input again.

It’s important to note that the continue statement only affects the innermost loop that it is in. If you have nested loops, you will need to use the continue statement multiple times to skip the current iteration in all of the loops.

In summary, break statement is used to exit a loop early, while the continue statement is used to skip the current iteration of a loop and move on to the next iteration. They both can be used infor and while loops, and can be useful when you have a certain condition that you want to check for, and if that condition is met, you want to skip the current iteration (with continue) of the loop or stop it completely (with break).

What’s next?

• If you found this story valuable, please consider clapping multiple times (this really helps a lot!)
• Hands-on Practice: Free Python Course — how to stop loops and how to skip an iteration
• Full series: 100 Days of Python
• Previous topic: While loops
• Next topic: How Python almost had another keyword