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8:01 with Lacey Williams Henschel

Learn how to transform Markdown text into HTML using a custom filter

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Teacher's Notes

mark_safe(variable) - Marks the variable as being safe to send directly to the browser without escaping or encoding the contents beforehand.

Markdown

Here's the markdown I used in the video:

## Testing is Amazing! 

Learn to test your Python applications with unittest and doctests! 

Things you will learn: 

- unittest 
- doctests

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We are almost done with customizing Django templates. 0:00

In real world scenarios you'll probably have users pasting long text 0:04

descriptions into your admin site using Markdown or another plain text format. 0:09

Markdown is what's used on GitHub for example, for read me files. 0:15

It allows you to easily type text that will render as html on a webpage, but 0:20

in Django you have to do some preparation to get that to happen as expected. 0:25

So let's write. 0:31

You guessed it, a custom filter for that. 0:32

First, we're going to install a Python library called markdown2. 0:37

In your console, change directories into learning site and 0:41

the run this command, pip install markdown2. 0:45

Okay. 0:50

Once that finishes running, open up course_extras.py and 0:51

add import markdown2 to the top. 0:56

Now, just to make sure everything's installed, let's start our server and 1:00

load our page. 1:04

If we don't get an import error, we know that everything installed correctly. 1:05

So we'll do python manage.py runserver, 1:10

and then identify our port. 1:16

Great. 1:19

It looks like we are good to go. 1:20

So let's create our function. 1:22

We'll put the console down here. 1:24

And then down here at the bottom, we'll call our function mark down to html. 1:27

And it's going to take an argument, 1:31

it'll take a markdown text as an argument. 1:36

It will return html, so we'll call what it returns html_body. 1:40

It's the stuff in the middle that we need to worry about. 1:47

So let's add a dock string, so 1:50

that everyone knows what this function is supposed to do. 1:51

So, converts markdown text to html. 1:54

That's pretty straightforward. 2:01

If we look at the documentation for markdown too. 2:03

We see that it's pretty simple. 2:06

We should be able to just call the mark down method on our passed in text, 2:08

and it will do all the processing for us. 2:13

I love simple libraries like this that are really powerful, and 2:16

do something amazing and useful, but don't require a lot of work on my part. 2:20

So let's add that to our function. 2:25

So we can say that html body is going to be equal to markdown2.markdown, 2:27

and then we pass in our markdown text. 2:34

So what this will do, is it will convert our markdown text into html and 2:38

store that result in our variable html body, which we then return. 2:43

Finally, we need to register our filter, and this is going to be exactly the same 2:48

as whenever we registered our time estimate filter. 2:54

The only thing we need to change is the name of the filter. 2:57

Markdown to html. 3:01

There we go. 3:04

Can you think of a place in our site where someone might 3:06

enter markdown text instead of regular html or plain text? 3:09

I can, the course description. 3:13

Sometimes those are longer and require some formatting. 3:16

So let's create a super user to log into the admin and 3:19

replace the current course description with some marked down text. 3:22

So down in your consul, stop your server with Ctrl+C. 3:27

And then run python manage.py createsuperuser. 3:31

I'm going to make my name Lacey, my user name. 3:37

And then I'll set my email address to Lacey@teamtreehouse.com. 3:40

My password, that's private. 3:47

Okay. 3:51

Let's restart our server, and 3:52

then head into the admin to edit a course description with some markdown text. 3:55

So up here in our url we just do /admin and 4:00

then we log in using those credentials that we just created. 4:05

Here in courses, I'm gonna change Python testing. 4:10

So right now it just says, learn to test your Python applications with unittest and 4:14

doctests. 4:18

I'm gonna replace this with some mark down text that I've created. 4:20

And we'll go over what those should do. 4:24

Okay. So I've added this header and 4:27

this double pound sign means that this line testing is amazing, 4:30

should appear inside the header tags. 4:34

Then, these next two lines learn to test your Python applications with unitest and 4:37

doctest and things you will learn should each show up inside their own P tags. 4:42

Then when you put a little dash next to a series of things that are in a list, 4:48

in html, this should render as an unordered list. 4:54

So now that we've done this, let's scroll down and save. 4:58

And let's head back into our course. 5:04

When we go to Python Testing, 5:06

it looks like those special mark down characters just rendered normally. 5:09

They didn't convert. 5:13

Oh, but that's because we forgot something important. 5:15

We forgot to add this filter that we created to our description, so 5:18

let's add that. 5:21

We ca go to the course_detail page and then we can just add our new 5:23

markdown_to_html filter. 5:28

Let's reload. 5:33

Oh, invalid filter. 5:35

Because up here with this load humanize, we also needed to load our course extras. 5:37

Now we can put load course extras on it's own line or 5:42

we can just stack it, next to humanize. 5:46

So let's do that to save ourselves some time. 5:49

Okay, this isn't quite what we expected. 5:51

We're seeing the actual html tags instead of the rendered html. 5:57

Now this is actually a nice thing that Django is doing for us. 6:03

It's Django's way of protecting us from code that might get plugged into our data 6:06

and might be malicious. 6:11

We just need to tell Django this code is safe, 6:13

meaning that it can render this html as html, with no problem. 6:16

For that, we can use the safe filter, so 6:21

we can chain safe next to markdown to html. 6:25

Now, when we reload the page, we get our nice, friendly rendered html. 6:31

There's a better way to mark text as safe though. 6:37

We should mark our output from the filter as safe, so 6:40

that anything that goes through this filter is marked safe and 6:43

we don't have to keep using the safe filter over and over again. 6:47

So let's import something called mark safe into course extras. 6:50

We can lower this console. 6:54

Go back up to the top and 6:57

from django.utils.safestring we import mark_safe, 7:01

and then we'll just pass our output into mark_safe as we return it. 7:09

Finally, we can go ahead and delete the safe filter from our variable. 7:17

Now when we refresh the page, we have the exact same result, 7:25

which is what we wanted. 7:28

In the real world, we do a few things differently. 7:29

We would probably have the user select the format that they were using to submit 7:35

their data, markdown, plain text, or something else, and 7:39

we'd use the appropriate conversion filter accordingly. 7:43

We would also add that filter to all the text content, 7:47

for example, to the step content, as well as to the course content. 7:51

But for our purposes, we've proven the concept, and that's enough. 7:56

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