1 00:00:00,000 --> 00:00:03,990 Here we have a simple database application that displays a list of random 2 00:00:04,000 --> 00:00:06,990 testimonials or quotes on a web page. 3 00:00:07,000 --> 00:00:09,990 If you look at my web page, I actually used this for testimonials. 4 00:00:10,000 --> 00:00:14,990 And every time the page gets reloaded, it pulls up three different quotes from 5 00:00:15,000 --> 00:00:16,990 the database at random. 6 00:00:17,000 --> 00:00:21,990 The database itself is managed with this application that allows you to go 7 00:00:22,000 --> 00:00:25,990 through and add, edit and delete entries in the database. 8 00:00:26,000 --> 00:00:28,990 We'll look at that in a separate movie in this chapter. 9 00:00:29,000 --> 00:00:33,990 In this chapter, we're going to look at how this application works ,which 10 00:00:34,000 --> 00:00:37,990 retrieves the quotes from the database and displays them at random. 11 00:00:38,000 --> 00:00:42,990 So in the Projects folder, in your Exercise Files, in the testimonials folder 12 00:00:43,000 --> 00:00:45,990 and you'll find testimonials.py. 13 00:00:46,000 --> 00:00:48,990 And this is actually exactly the same script that is on my web site. 14 00:00:49,000 --> 00:00:53,990 This is the script that reads the quotes from the database and displays a 15 00:00:54,000 --> 00:00:53,990 number of them at random. 16 00:00:54,000 --> 00:00:56,990 It's a very short script. 17 00:00:57,000 --> 00:01:01,990 It's just 73 lines long, including the white space and comments and everything, 18 00:01:02,000 --> 00:01:02,990 and here's how it works. 19 00:01:03,000 --> 00:01:08,990 The first thing it does is it initializes some variables. 20 00:01:09,000 --> 00:01:11,990 It reads the configuration file to find out where the database is and 21 00:01:12,000 --> 00:01:14,990 everything, and opens up the database. 22 00:01:15,000 --> 00:01:18,990 And all that happens here in this init function. 23 00:01:19,000 --> 00:01:23,990 Here it reads the configuration file there and it opens up the database here. 24 00:01:24,000 --> 00:01:29,990 And this uses libraries that I've also included in the Lib folder. 25 00:01:30,000 --> 00:01:37,990 bwDB for my normalized CRUD oriented database functions, and bwConfig for 26 00:01:38,000 --> 00:01:38,990 reading the configuration file. 27 00:01:39,000 --> 00:01:42,990 bwConfig is a very simple library. 28 00:01:43,000 --> 00:01:46,990 It reads these configuration files in a format that I had already been using for 29 00:01:47,000 --> 00:01:50,990 a long time with my Perl work from before I was working on Python. 30 00:01:51,000 --> 00:01:53,990 And so I just wanted something that would read the same configuration file, so I 31 00:01:54,000 --> 00:01:57,990 could start replacing a lot of my Perl scripts with Python scripts, and it was 32 00:01:58,000 --> 00:02:00,990 just very easy for me to write that. 33 00:02:01,000 --> 00:02:05,990 And the application itself mostly takes place in this one function, in main. 34 00:02:06,000 --> 00:02:09,990 The first thing it does is it goes out to the database and it grabs a list of 35 00:02:10,000 --> 00:02:16,990 all the IDs, and it does this with this sql_query method which returns a 36 00:02:17,000 --> 00:02:20,990 generator which iterates through the results. 37 00:02:21,000 --> 00:02:29,990 And iterating through results, I simply take all of these IDs and add them to this list here. 38 00:02:30,000 --> 00:02:33,990 I'm using a list because I need to be able to delete things from it later. 39 00:02:34,000 --> 00:02:35,990 So a tuple would have been immutable. 40 00:02:36,000 --> 00:02:39,990 Then I want to know how many records I'm going to be displaying and so I 41 00:02:40,000 --> 00:02:45,990 look for the query string and if there isn't a query string, that just default to five. 42 00:02:46,000 --> 00:02:53,990 And we'll notice, if we look at the HTML for the page that has those quotes on it, 43 00:02:54,000 --> 00:02:58,990 you'll notice this is called with this little bit of server side include and 44 00:02:59,000 --> 00:03:04,990 so it's called testimonials.py with a query string set to 3. 45 00:03:05,000 --> 00:03:08,990 And so, that's why we have three of them displaying on that page. 46 00:03:09,000 --> 00:03:12,990 And then, I check and see if we have enough in the database to be able to 47 00:03:13,000 --> 00:03:14,990 display a decent number randomly. 48 00:03:15,000 --> 00:03:18,990 I like further to be at least four times as many records in the database as 49 00:03:19,000 --> 00:03:21,990 those that I am displaying. Otherwise I really don't want to bother doing 50 00:03:22,000 --> 00:03:26,990 something random because it's not going to look random. 51 00:03:27,000 --> 00:03:35,990 Now we simply take the list of IDs and using the random library, which gets 52 00:03:36,000 --> 00:03:37,990 imported up at the top here. 53 00:03:38,000 --> 00:03:41,990 This is in the standard Python library. 54 00:03:42,000 --> 00:03:48,990 It creates a random integer based on the size of the list minus one, and it 55 00:03:49,000 --> 00:03:54,990 grabs a random item from the list of IDs, and then it deletes that from the list 56 00:03:55,000 --> 00:04:00,990 and adds it to the list of result IDs, which is initialized here. 57 00:04:01,000 --> 00:04:03,990 Then once it has that list of result IDs, 58 00:04:04,000 --> 00:04:07,990 it simply iterates through that list and prints the record with that ID. 59 00:04:08,000 --> 00:04:12,990 And printing a record with that ID, it uses the CRUD function getrec and then 60 00:04:13,000 --> 00:04:17,990 it simply grabs the data out of the resulting row factory, indexing on it as if 61 00:04:18,000 --> 00:04:18,990 it were a dictionary. 62 00:04:19,000 --> 00:04:20,990 We'll go ahead and run this here. 63 00:04:21,000 --> 00:04:27,990 Well for our purposes, we're going to need to reduce this little default down to a three. 64 00:04:28,000 --> 00:04:33,990 So I'll save that and run it, and here we have our result. 65 00:04:34,000 --> 00:04:39,990 We have three quotes, and if we run it again, we get three different quotes and 66 00:04:40,000 --> 00:04:45,990 different quotes and you'll notice that it's all coming out in HTML. 67 00:04:46,000 --> 00:04:48,990 So, that's how this application works. 68 00:04:49,000 --> 00:04:52,990 Once we have done the back end work of creating the CRUD, once we have done the 69 00:04:53,000 --> 00:04:58,990 back end work of creating a decent library with easy to use database interface, 70 00:04:59,000 --> 00:05:02,990 writing something like this becomes relatively trivial. 71 00:05:03,000 --> 00:05:13,000 And so, here we have it on the webpage with our random quotes.