WEBVTT 00:00.120 --> 00:02.120 And a warm welcome back to cursor. 00:02.280 --> 00:07.840 And also we are coming now into week four Landgraf and into lab one. 00:08.120 --> 00:11.520 And it's not only welcome back to cursor, it's also welcome back to notebooks. 00:11.560 --> 00:14.680 You know I love these things I know the mixed mixed popularity. 00:14.960 --> 00:16.640 Uh with with with others. 00:16.640 --> 00:18.640 But but hopefully you'll put up with them for a bit. 00:18.680 --> 00:20.320 We'll use code as well this week too. 00:20.360 --> 00:21.040 Don't worry. 00:21.440 --> 00:25.680 So we're going to start by doing some imports as we get started. 00:25.680 --> 00:28.360 And then we also have some constants. 00:28.360 --> 00:29.360 Ignore these for now. 00:29.400 --> 00:30.600 We'll use them in a bit. 00:30.640 --> 00:31.320 They're silly. 00:31.680 --> 00:35.520 Uh and we're also going to have our favorite, uh, little thing here. 00:36.120 --> 00:39.360 And you may be wondering why we didn't have that during crew week. 00:39.480 --> 00:40.680 It was absent. 00:40.840 --> 00:43.560 And the reason is that crew just does that for you automatically. 00:43.600 --> 00:48.240 Crew uses the env file itself, and so you don't need to run it. 00:48.800 --> 00:49.280 Okay. 00:50.120 --> 00:54.280 Now I need to explain something called annotated. 00:54.520 --> 01:00.520 So hopefully you're somewhat familiar with things called type hints in Python, an optional feature 01:00.520 --> 01:03.080 that is often used in engineering. 01:03.480 --> 01:09.360 To give you an example, supposing that we have a Python function called shout that takes some text, 01:09.760 --> 01:16.720 and the job of shout is to print the text in uppercase. 01:17.000 --> 01:18.280 That seems fairly simple. 01:18.600 --> 01:22.800 And let's just shout hello like that. 01:23.600 --> 01:25.080 Hopefully no surprise. 01:25.080 --> 01:27.760 Hello in capitals comes up. 01:28.120 --> 01:35.240 Well, uh, the type hints is when you are clear to Python, uh, what is the type of variable that 01:35.240 --> 01:36.280 you're using at each point. 01:36.280 --> 01:39.920 So you can say that that text is a string by putting colon str. 01:40.200 --> 01:46.040 And you can put here that will return a string or it's not returning anything, it's returning none. 01:46.040 --> 01:49.240 But if we also have it, uh, if we leave it like this, oops. 01:49.400 --> 01:53.520 If we have it be returning a string, then it will be unhappy. 01:53.520 --> 01:57.120 But we would need to then also return text upper as well. 01:59.560 --> 02:00.440 And then it will run. 02:00.440 --> 02:02.000 So these are called type hints. 02:02.000 --> 02:05.810 And they are a useful way of specifying what's going on. 02:06.050 --> 02:13.050 There is a feature that you can use called annotated in which we could type annotated. 02:15.210 --> 02:16.570 String comma. 02:16.570 --> 02:19.010 And then we can put some message here. 02:19.330 --> 02:23.410 Uh, something to be shouted. 02:24.690 --> 02:28.370 Uh, and this is something I need to close the square brackets. 02:28.490 --> 02:30.410 This is just extra information. 02:30.410 --> 02:33.690 That's a sort of FYI that's included in here. 02:33.810 --> 02:36.130 Uh, Python doesn't make any use of this at all. 02:36.130 --> 02:42.170 But if we are going to provide this function to, to, to another platform or in some other context, 02:42.170 --> 02:46.090 someone might want to read how we've annotated it, and that might be useful for someone. 02:46.090 --> 02:51.090 So annotations can be used for this purpose of kind of tagging variables to have a purpose. 02:51.090 --> 02:52.810 So this should run without any change at all. 02:53.050 --> 02:54.690 That is completely ignored. 02:54.890 --> 03:00.370 Uh, and it's just just a useful way of adding some extra information in case, in case it matters to 03:00.410 --> 03:03.290 somebody else and it is going to matter to somebody else. 03:03.330 --> 03:07.250 Landgraf is going to want us to annotate, in order to tell it something. 03:07.250 --> 03:08.330 Let's come on to that. 03:08.330 --> 03:13.050 So I explain here again, you could have a variable like my favorite things that could be a list. 03:13.330 --> 03:17.170 And you could say that my favorite things, you could actually not just describe it as a list, but 03:17.170 --> 03:18.570 say that it is annotated. 03:18.570 --> 03:19.530 It's a list. 03:19.530 --> 03:25.770 And these are a few of mine I added as an annotation to my favorite things. 03:26.090 --> 03:28.490 Uh, so why do I tell you this? 03:28.530 --> 03:32.050 Well, it all comes back to these things called reducers. 03:32.370 --> 03:35.730 We are about to define our state object. 03:35.770 --> 03:38.050 And when we do so we're going to give it a few fields. 03:38.050 --> 03:40.570 And when we define those fields we have to give them a type. 03:40.890 --> 03:47.570 And when we give them a type, we don't just specify the type, but we use annotated to be able to specify 03:47.610 --> 03:48.690 a reducer. 03:48.930 --> 03:55.610 If Landgraf is expected to use a reducer, that is the technique use annotated to do that. 03:55.810 --> 03:57.970 Um, and that that is what we're going to do. 03:58.210 --> 04:03.010 And as it happens, Landgraf comes with with one out of the box that's very useful for us called Add 04:03.010 --> 04:03.770 Messages. 04:03.970 --> 04:06.450 Uh, and that is one that I just imported up here. 04:06.450 --> 04:10.170 So if you look up here, one of my imports was from Landgraaf. 04:10.810 --> 04:13.130 Message import add messages. 04:13.130 --> 04:15.010 So that is it's like a function. 04:15.010 --> 04:18.010 And it's a function that you can, you can annotate with. 04:18.050 --> 04:21.250 If you want to say, hey this is the reducer I'd like you to use. 04:21.730 --> 04:26.650 So to make this feel real let me just let's go ahead and define our state. 04:26.650 --> 04:32.290 So you remember step one in the in the puzzle is to define the state object. 04:32.290 --> 04:33.570 That is what we're doing here. 04:33.570 --> 04:35.250 We are going to have a state object. 04:35.450 --> 04:36.410 Now state objects. 04:36.410 --> 04:37.530 You can define them in many ways. 04:37.530 --> 04:39.890 They can in fact be any Python object that you want. 04:40.170 --> 04:46.290 It's most common to either have it be a Pydantic object that we met in the last week. 04:46.530 --> 04:47.410 Uh, it can be. 04:47.450 --> 04:48.730 Or we made it the last two weeks. 04:48.850 --> 04:52.850 Uh, it can be a pydantic object, meaning it's a subclass of base model. 04:52.850 --> 04:59.090 It can also be something called a typed dict, which is a particular type of, of dictionary in Python 04:59.090 --> 05:01.210 where you specify what the keys need to be. 05:01.530 --> 05:07.130 Uh, but but it can also be anything but it is quite common to use either pydantic objects or type dicts 05:07.130 --> 05:10.250 and we will use Pydantic, since that's something that we're familiar with. 05:10.290 --> 05:15.090 So we are going to have a state object defining the state of our system. 05:15.090 --> 05:19.010 And it only has one field and that's called messages. 05:19.010 --> 05:22.050 And that is going to store in it a list of messages. 05:22.050 --> 05:25.250 And these this list of messages is going to be passed around our graph. 05:25.250 --> 05:28.490 And over time it's going to build up as messages get added to it. 05:28.930 --> 05:32.210 And so we are going to say that it's it's something that's annotated. 05:32.210 --> 05:33.170 It is a list. 05:33.170 --> 05:36.930 So it consists of a list of things of messages. 05:37.530 --> 05:42.650 And we are going to then because we're annotating it, we can provide an annotation that's ignored by 05:42.650 --> 05:45.130 Python, but it can be used by Landgraf. 05:45.330 --> 05:52.130 And that annotation is where we get to specify the reducer, the function that will be called in order 05:52.130 --> 05:54.850 to combine one state with another. 05:55.050 --> 05:58.610 And we're going to use one out of the box called Add messages. 05:58.610 --> 06:02.650 It is a reducer that is used to add messages. 06:02.650 --> 06:03.770 And it's very simple. 06:03.770 --> 06:04.810 It's very vanilla. 06:04.970 --> 06:07.770 All it does is it assumes this is a list. 06:07.770 --> 06:11.060 And if you return something with with an and items in the list. 06:11.100 --> 06:16.420 It just combines it with everything else in the list before it concatenates these lists together. 06:16.540 --> 06:17.860 That's all it does. 06:18.220 --> 06:20.540 So hopefully that makes a bit of sense. 06:20.940 --> 06:25.860 Uh, if not, then you'll see it'll become clear as we use this exactly what's going on. 06:25.900 --> 06:30.500 And and why were the use of this and the reducer and how it's working. 06:30.780 --> 06:32.780 So step one we define the state object. 06:32.820 --> 06:35.900 Step two we start the graph builder. 06:35.900 --> 06:39.660 And that is just a matter of calling this thing called state graph. 06:39.660 --> 06:43.100 Instantiating a state graph passing in state. 06:43.220 --> 06:47.100 And one thing to to get your head around here is that what I'm passing in there. 06:47.100 --> 06:48.260 The thing I've just highlighted. 06:48.260 --> 06:50.460 It's not an object I'm not instantiating. 06:50.460 --> 06:55.580 I'm not I'm not creating a state and passing that in with with messages and so on. 06:55.620 --> 06:57.500 Now I'm passing in the class. 06:57.620 --> 07:01.340 I'm passing in the type of thing that represents our state. 07:01.340 --> 07:04.900 That is what I'm using to create my state graph. 07:04.900 --> 07:07.940 And this is beginning the graph building process. 07:08.060 --> 07:12.580 This is part of the five steps before we actually run our Agentic framework.