Loop Control: break, continue, & else

Sometimes, the standard “top-to-bottom” execution of a loop isn’t enough. You might need to stop early because you found what you were looking for, or skip a specific record that contains invalid data.

Python provides four tools for fine-tuning loop behavior: break, continue, pass, and the powerful (but often misunderstood) else clause.

1. `break`: The Emergency Exit

The break statement immediately terminates the innermost loop and jumps to the first line of code after the loop block.

# Find the first multiple of 7 in a list
data = [12, 18, 21, 28, 30]

for num in data:
    if num % 7 == 0:
        print(f"Found it: {num}")
        break # Stop the loop entirely

Under the Hood

When Python hits break, it discards the loop’s iterator and moves the “Instruction Pointer” to the end of the loop’s bytecode. This is an extremely efficient way to stop processing.

2. `continue`: The Skip Button

The continue statement stops the rest of the current iteration and jumps back to the top of the loop for the next cycle.

emails = ["alice@gmail.com", "", "bob@yahoo.com", "invalid-email"]

for email in emails:
    if not email or "@" not in email:
        continue # Skip to the next email
    send_notification(email)

Note: In a for loop, continue fetches the next item. In a while loop, it re-evaluates the condition.

3. `pass`: The Placeholder

pass is a null operation. It literally does nothing. Because Python uses indentation to define blocks, you cannot have an “empty” block.

def process_data(data):
    for item in data:
        if item.is_valid():
            # TODO: Implement processing logic
            pass
        else:
            log_error(item)

Context: Use pass as a temporary placeholder while sketching out your program’s structure.

4. The Loop `else` Clause (Deep Dive)

This is one of Python’s most “hidden” features. An else block attached to a loop behaves differently than an else attached to an if.

Rule: The else block executes ONLY if the loop completed naturally (i.e., it was NOT terminated by a break).

The “Search and Handle” Pattern

This is the most common professional use for the loop-else. It allows you to handle the “Not Found” case without using a “flag” variable.

Old Way (Flag Variable)
Pythonic Way (Loop-Else)

found = False
for x in data:
    if x == target:
        found = True
        break
if not found:
    print("Not found")

for x in data:
    if x == target:
        print("Found!")
        break
else:
    # This only runs if the loop finishes
    # without finding the target!
    print("Not found")

5. Summary Table

Statement	Effect on Loop	Next Action
`break`	Terminates loop.	Jumps to code after the loop.
`continue`	Skips current iteration.	Jumps back to start of loop.
`pass`	No effect.	Continues with next line in block.
`else`	Logic for completion.	Runs if no `break` occurred.

Loop Control: break, continue, & else

1. break: The Emergency Exit