Break and Continue

We learned for and while. Loops do their job from start to finish. But what if, in the middle of a loop, we want to say "ok, that's enough, stop"? Or "skip this one, go to the next"?

For exactly these two situations, Python gives us break and continue

break stops the loop completely. Once we hit it, the program exits the loop, no matter how many iterations were left

i = 0
for i in range(0, 100):
    if i == 5:
        break
    print(i)

Output

0
1
2
3
4

We told for to go from 0 to 99, but as soon as i became 5, we hit break and the loop stopped. The numbers 5, 6, 7, ..., 99 were never printed

A real example: imagine we scan the station's sectors, one by one, to find a signal. Once we found it, why keep scanning?

for sector in range(1, 100):
    if sector == 7:
        print(f"Signal found in sector {sector}!")
        break
    print(f"Scanning sector {sector}...")

Output

Scanning sector 1...
Scanning sector 2...
Scanning sector 3...
Scanning sector 4...
Scanning sector 5...
Scanning sector 6...
Signal found in sector 7!

The loop never checked sectors 8 through 99, because we already found what we wanted. break saved us time

continue is different. It doesn't stop the loop. It just skips the rest of the current iteration and jumps to the next one

i = 0
for i in range(0, 10):
    if i == 5:
        continue
    print(i)

Output

0
1
2
3
4
6
7
8
9

Notice that 5 is missing. When i was 5, continue kicked in, jumped over print(i), and the loop kept going from i = 6

A real example: print only even numbers from 0 to 10

for i in range(0, 11):
    if i % 2 != 0:
        continue
    print(i)

Output

0
2
4
6
8
10

For odd numbers, continue skipped the print. For even ones, the if was False, so continue didn't fire and print ran normally

Both keywords work the same way in while loops, not just for. A very common pattern is while True together with input(): we repeat forever and exit with break when the user tells us to

while True:
    command = input("Command: ")
    if command == "stop":
        break
    print(f"Running: {command}")
print("System stopped")

while True would normally be an infinite loop. But on every step we ask for a command, and if the user types stop, break takes us out of the loop. Whatever else they type, the program prints Running: ... and asks again

Notice command == "stop". So far we've only used == with numbers, but it works just as well with text: command == "stop" is True only if the variable holds exactly the word stop. Text comparison is case-sensitive, so "Stop" or "STOP" would be different from "stop"

Mission: Manual Sector Scanner

The station operator enters sector numbers one by one. Use a while True loop and read a number on every step with int(input(...)). For each number:

• if the operator types 0 → it's the end of the scan, stop the loop (use break)
• if the number is negative → it's just noise, skip it (use continue) and print nothing
• otherwise → print Sector then the number, then checked (for example Sector 4 checked)

After the loop, print Scan complete.

Example

If the operator types 4, then -2, then 7, then 0 in turn, the program prints

Sector 4 checked
Sector 7 checked
Scan complete

-2 is skipped, and 0 stops the scan.