Customizing Attributes

If you've taken customizing Django templates, you might remember writing 0:00 a custom filter that estimated how long it would take someone to complete a course, 0:04 based on how many words were in the course description. 0:09 It's not the most scientific method of estimating time to completion, but 0:12 that's fine. 0:16 Now we're going to use the same function we wrote in that course 0:18 to add a custom attribute to our model that will then display in the admin. 0:21 Remember that custom template tags are just regular Python functions, so 0:27 we can import that function into another module and use it. 0:31 So, let's get started. 0:35 Open up course_extras.py. 0:37 So you see this function here time_estimate? 0:42 This is the function we're going to be using. 0:45 Now if you scroll to the top, you'll see that we're all ready importing 0:48 the course.models into course_extras, which is great. 0:52 We don't wanna change that. 0:56 But it makes things a little tricky when we import this function 0:58 into our models.py file. 1:02 Since we're going to be importing time_estimate from coarse_extras.py into 1:03 models.py., but since course_extras.py is all ready importing one of the models, 1:08 we would get an error if we added the import statement to the top of models.py. 1:14 Basically, we'd be trying to do a recursive import and 1:19 Python would be, what? 1:23 So instead, let's go into the course model and add our method, 1:25 which we will call time_to_complete and 1:29 then we'll add the import statement directly inside this method. 1:32 This will get us around any sort of recursive import errors that we 1:35 might encounter. 1:39 So we define time_to_complete and then we add the import statement. 1:41 So, from courses.templatetags.course_extras 1:47 import time_estimate. 1:55 We'll also want to return the result of calling the time_estimate function, 2:00 so we can go ahead and add that as well. 2:05 Awesome. 2:07 Now, remember that time estimate is based on the number of words. 2:09 So, we need to pass in the number of words or 2:13 the word count of the course description into the time_estimate function call. 2:16 Whenever we did this in customizing Django templates, 2:21 we got the word count using one of Django's built-in filters. 2:24 But in models.py, we don't have access to that. 2:28 Instead, we can get out the word count using a combination 2:31 of the built in Python functions len and split. 2:35 So, we'll just get the length of self.description but 2:39 that's just going to give us the character count or the byte count. 2:45 So instead, we add split and then that will get us the word count. 2:48 So save that, and now all we need to do is add the time to 2:54 complete attribute to the list display in our CourseAdmin class. 2:59 So, we go into admin.py and right here in the CourseAdmin, 3:03 inside the list display variable, we just add time_to_complete. 3:08 All right, save that and then start your server, 3:14 if it's not all ready started, and refresh your courses list. 3:18 And now you see that we have these numbers underneath time to complete, and 3:24 remember, these numbers stand in for minutes. 3:27 Now, one quick caveat. 3:30 When I refreshed mine the first time, 3:32 all I got was 0 minutes across the board because our descriptions are so short. 3:34 So, I went into a couple of courses, and I replaced the course description with 3:39 some sort of fun dessert-themed lorem ipsum text just to bulk up the word 3:43 count in the description and illustrate how the time to complete would work. 3:48 So feel free to Google, like fun lorem ipsum and 3:53 experiment with this for yourself. 3:56 But as you can see, a number all by itself like this this random 14 or this 25, 3:59 is not super helpful. 4:04 It's useful to have the unit of measurement, like the minutes. 4:06 And so we can add this to the method on our model to return the minutes. 4:10 So, we can return this whole thing as a string. 4:14 So, if we go back into models.py and we add some things to this return statement. 4:17 So we open up a string and then we add these brackets and 4:23 then min and close the string and then we add format and 4:28 we enclose the whole rest of this line inside the format call. 4:32 And we refresh our page. 4:39 Then we have the minutes added so we can see that Ruby Basics takes 14 4:42 minutes versus Python testing, which apparently takes no time at all. 4:46 That looks a lot better. 4:50 Great work. 4:52 As you can see, adding custom attributes to your list view 4:54 is as easy as writing a little method to bring back the information you need and 4:57 then adding it to your admin class. 5:02 Now, we've got this handy piece of information at our fingertips. 5:04 We could even use this to add an extra filter to this page. 5:08 Why don't you try that on your own? 5:12