How can you interrupt the execution of a loop in Python?

To interrupt the execution of a loop, the break and return statements are used, as well as exception handling.

break terminates the nearest enclosing loop (for, while) and transfers control to the statement following the loop.

# Example of using break
for i in range(10):
    if i == 5:
        break # Interrupts the loop at i = 5
    print(i)

return terminates the execution of a function or method and returns a value. If the loop is inside a function, return will interrupt both the loop and the function execution.

# Example of using return in a function with a loop
def find_item(items, needle):
    for item in items:
        if item == needle:
            return item # Interrupts the loop and the function, returning the found item
    return None # If the item is not found after the loop

result = find_item([1, 2, 3, 4, 5], 3)
print(result)

Exceptions can be used to interrupt loop execution, especially if the break condition arises due to an error or special state.

# Example of interrupting a loop with an exception
class CustomInterrupt(Exception):
    pass

try:
    for i in range(10):
        if i == 7:
            raise CustomInterrupt("Interrupt on condition")
        print(i)
except CustomInterrupt as e:
    print(f"Loop interrupted: {e}")

Summary table of methods:

Method	Scope of action	Purpose
break	Nearest enclosing loop	Interrupts the loop
return	Function/method (including nested loops)	Interrupts the function/method and returns
Exception	Current try/except block or higher	Error handling or special conditions