Python has some special commands,
pass, that give you
more control over your loops and blocks.
break command allows you to exit a loop prematurely.
while True: favorite_food = raw_input('What is your favorite food?') if favorite_food == 'broccoli': print "We are through here!" break print "That's a good one! Let's see what your friends think"
You would obviously want to place the break command inside of a conditional
statement like the loop above. One thing you might notice is that we could avoid
using the break command in the example loop by simply setting a
variable and then placing the last
likes_broccoli = False while not likes_broccoli: favorite_food = raw_input('What is your favorite food?') if favorite_food == 'broccoli': print "We are through here!" likes_broccoli = True else: print "That's a good one! Let's see what your friends think"
We can often avoid the
break command with some careful structuring but it is
sometimes really handy to use which is why we are learning about it.
continue command allows you to continue the next iteration without
covering the rest of the block. The following example prints all of the numbers
from 1 to 20 except those that are multiples of 3. It uses the
operator to find out which ones are multiples of 3.
for num in range(1, 21, 1): if num % 3 == 0: continue print num
We could restructure this example just like we did with the
break example so
that we wouldn't have to use the
continue command by putting the if statement
around the print.
for num in range(1, 21, 1): if num % 3 != 0: print num
Again, you should often be able to avoid using the command but it can come in handy.
pass command is what we call a noop (pronounced NO-op and means that there
is no operation). You might be wondering why you would want something that does
nothing in your code. What the
pass command allows you to do is stub your code
out. There are times where you know that you are going to use an if statement
but don't know what to do in the block.
if something_cool_happens: pass
If we didn't put
pass in the if statement above, the program would not be able
to run. The
pass simply allows us to write a program that compiles.
Try writing some loops that break out early and continue based on some of your own conditions!