Modern APIs with FastAPI and Python Transcripts
Chapter: Building our first API
Lecture: Passing data to the API

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0:00 So our calculator API is working.
0:03 If we open it up down here,
0:04 let's see what we got. Remember,
0:06 we have a not found, but if we go to "api/calculate" we're getting
0:09 this data back and it's 4.
0:11 Well, how exciting and how generally useful is this calculator?
0:15 Not at all, right? All we're ever going to get is 4.
0:18 So the answer is always 4. Maybe it should have been 42, but 4 it is.
0:21 So let's go and change this so we can pass some data in.
0:25 Now let's say we take an "x, y, and z",
0:29 those are the three things we could pass in, and the value is gonna be
0:33 "x + y" like, for now we'll do times, maybe we'll do divide,
0:37 It will let us do something slightly more interesting in just a moment. So we could
0:41 go over here, and if we run this again,
0:43 we come up and say
0:44 "?x=2&y=3&z=10"
0:49 What are we going to get here?
0:50 Are we going to get, what did we say?
0:52 X plus y is 5, and then times 10 it should be 50, are we gonna get 50?
0:56 Let's find out. No,
0:58 we got nothing. So we cannot multiply sequence by a string.
1:03 Wait a minute. What's going on here?
1:04 Let's take away the Z for a minute.
1:06 Try that again. 23, 23 as a string.
1:10 If you look at it real careful,
1:11 notice right here, there are quotes, that is not an integer
1:14 in JSON, that is a string.
1:16 So what's the problem? The problem is,
1:18 everything passed around on the Web is strings by default.
1:22 But something needs to say "no,
1:23 no, no. We expect this to be an integer".
1:26 So if I go over here and I change this and I use type hints, you
1:30 say this is an integer and this is an integer and we say this
1:34 is an integer. Let's do this again.
1:36 Also notice it didn't say anything about any of these values being required.
1:41 But now, let's try it again.
1:43 Well check it out. We got the value
1:44 5, and if we look at the raw data,
1:47 it doesn't have quotes, it's really 5.
1:48 And let's go back here and put our times z, run it again,
1:52 Yes, we got 50. Okay,
1:54 this is working pretty well. What happens if I omit Z?
1:59 Look at that. We got an error message and if we actually look exactly what
2:01 we got, it says "there's something wrong with the query string" and there's a Z
2:06 that's supposed to be in there.
2:07 But there's no Z in the query string,
2:08 but we expected one, and the problem is the Z is required and the type
2:12 of errors is that it's missing. So let's put our Z back.
2:18 Okay, so you're gonna see when we pass these over,
2:20 If there's no default value and there's no optional value,
2:23 things like that, these become required.
2:25 But we could say over here that this is a 10.
2:29 Here we go. Now, we don't have to specify the Z because there's a
2:32 default value for it. But if we do for the omit
2:35 the y where there is no default value then hey,
2:36 guess what? y is missing.
2:38 We gotta pass it over. Alright,
2:39 cool. So this is how we pass data at least from the query string as
2:44 well as you would see the path, like we could do like X,
2:47 Y like this and make that part of the URL, doesn't have to be the query
2:51 string, and you would be doing this exactly the same way.
2:54 Okay, so this is how we pass data over to our API method.