1 00:00:00,000 --> 00:00:03,990 Sometimes when you are writing a loop you need a way to shortcut the loop, or to 2 00:00:04,000 --> 00:00:07,990 break out of the loop, and Python has controls for this. 3 00:00:08,000 --> 00:00:14,990 Let's go ahead and make a working copy of loopcontrol.py. I'll call this 4 00:00:15,000 --> 00:00:18,990 loopcontrol-working.py and go ahead and open that working copy. 5 00:00:19,000 --> 00:00:22,990 Here, we have a simple loop that prints out each character of a string. 6 00:00:23,000 --> 00:00:25,990 It looks like it's just printing the string, but it's actually doing it one 7 00:00:26,000 --> 00:00:27,990 character at a time in the loop. 8 00:00:28,000 --> 00:00:30,990 I'll go ahead and run this, and you'll see that's what it looks like. 9 00:00:31,000 --> 00:00:37,990 Let's say that we wanted to skip all of the letter Ss. We could simply say if c =='s': 10 00:00:38,000 --> 00:00:39,990 and continue. 11 00:00:40,000 --> 00:00:42,990 What continue does is it shortcuts the loop. 12 00:00:43,000 --> 00:00:46,990 It just goes back to the beginning and gets to the next iteration without doing 13 00:00:47,000 --> 00:00:48,990 whatever comes after it. 14 00:00:49,000 --> 00:00:52,990 If we save this and run, we see that we skip all the Ss. 15 00:00:53,000 --> 00:00:55,990 On the other hand, maybe we want to end at the first s. Maybe we were 16 00:00:56,000 --> 00:01:01,990 just looking for the first s. So, we can use break, and break jumps out of loop entirely. 17 00:01:02,000 --> 00:01:02,990 Let me save this and run it. 18 00:01:03,000 --> 00:01:04,990 That terminates the loop. 19 00:01:05,000 --> 00:01:09,990 It just brings the first 3 characters, and when it gets that first s, it stops entirely. 20 00:01:10,000 --> 00:01:11,990 So, that's break and continue. 21 00:01:12,000 --> 00:01:15,990 Finally, there is one more control in Python. 22 00:01:16,000 --> 00:01:20,990 It's called else, and it works just like else does in an if statement. 23 00:01:21,000 --> 00:01:27,990 If I say else here, and print ('else') and get rid of this break, 24 00:01:28,000 --> 00:01:32,990 what this does is this gets run whenever this condition becomes completely false. 25 00:01:33,000 --> 00:01:37,990 In other words, when the iterator is out of stuff to iterate, then else gets used. 26 00:01:38,000 --> 00:01:42,990 So, if I save this and run it, you see that it prints the entire string and 27 00:01:43,000 --> 00:01:43,990 then it prints else. 28 00:01:44,000 --> 00:01:49,990 And else also works in a while loop - actually all of these controls also work in while loop. 29 00:01:50,000 --> 00:01:52,990 I am just going to show you this one. I am going to do this as a while loop 30 00:01:53,000 --> 00:01:59,990 here, we'll say i= 0 and while (i 00:02:05,990 We don't have this c here any more. We can say s so i, and then we'll need to increment. 32 00:02:06,000 --> 00:02:08,990 All right, here we go. 33 00:02:09,000 --> 00:02:13,990 So, let's save this and run it, and we see that does exactly the same thing. 34 00:02:14,000 --> 00:02:16,990 So, when this condition becomes false, in other words when we've 35 00:02:17,000 --> 00:02:21,990 incremented past the end of the string, then else gets used, and it prints 36 00:02:22,000 --> 00:02:22,990 the else down there. 37 00:02:23,000 --> 00:02:29,990 So, that's break and continue and else, and these are controls that will break 38 00:02:30,000 --> 00:02:30,990 entirely out of loop. 39 00:02:31,000 --> 00:02:35,990 will shortcut a loop with continue, or else is used when the condition becomes 40 00:02:36,000 --> 00:02:39,990 completely false, or if it's never true in the first place. 41 00:02:40,000 --> 00:02:50,000 So, that's break, continue and else.