[python] Python: 'break' outside loop

in the following python code:

narg=len(sys.argv)
print "@length arg= ", narg
if narg == 1:
        print "@Usage: input_filename nelements nintervals"
        break

I get:

SyntaxError: 'break' outside loop

Why?

Because the break statement is intended to break out of loops. You don't need to break out of an if statement - it just ends at the end.

This is an old question, but if you wanted to break out of an if statement, you could do:

while 1:
    if blah:
        break

break breaks out of a loop, not an if statement, as others have pointed out. The motivation for this isn't too hard to see; think about code like

for item in some_iterable:
    ...
    if break_condition():
        break 

The break would be pretty useless if it terminated the if block rather than terminated the loop -- terminating a loop conditionally is the exact thing break is used for.

Because break can only be used inside a loop. It is used to break out of a loop (stop the loop).