[SOUND] You've made it to the last stage of this course,

but it's not time to celebrate just yet.

We still have a few more things to learn before you finally get your shiny new

Django templates badge.

In this video, we're going to build our own custom template filter

that we can use on variables just like built-in filters.

Remember, a filter is something that you can add to a Django template variable

with the pipe character, that helps make the data in your template more dynamic.

In the case of the pluralized filter,

you learned in another video that it can automatically make a word plural

based on the value of a numeric variable in the template.

So let's write a filter that will help us estimate how much

time a step in a course will take to complete.

So let's open up the file we've been keeping our custom template tags in,

course_extras.py.

This is where we'll also be adding our custom filter.

Make a new function called, time_estimate, and have it take in a value.

So, define time_estimate, and I'm going to call my value, word_count.

In our case, this value will be a number, the number of words in a steps content.

This filter is not going to be super scientific.

This is mostly a thought exercise.

But let's say that the longer a steps content is,

the more content we think it covers and the more time we think it will take.

So with that in mind, let's say that for every 20 words in a steps content,

we think it will take that many minutes to complete the course.

So let's code that.

So minutes = round(word_count/20).

We're using the round function here, which is a built-in Python function, so

we get a nice even number.

We don't want to display 5.4567 minutes, do we?

This is just an estimate.

So we estimate that for every 20 words in a word count,

it will take about a minute to complete that part of the step.

Now, we just need to return the minutes.

And we should add a docstring so

that everyone else who looks at our code knows what this filter does.

So we can say, Estimates the number of minutes it will take

to complete a step based on the passed-in wordcount.

Finally, we need to register the filter.

Registering filters is almost the same as registering tags.

We use the decorator, and then instead of saying .inclusiontag or .simpletag,

we just say .filter and pass in the name of our filter.

Now we can try it out.

If we pop over to step detail, we can load our

course_extras so that we have access to our brand new filter.

But wait a second, we don't have a variable for

the word count that we've passed-in from our view.

Let's see what we can do about that in the next video.

Well, we made our filter but we need to figure out how to use it.

Are you thinking what I'm thinking?

What if there's a way we can use the built-in word count filter

to get the data we need for this filter?

Let's find out in the next video.