Use a basic HTML template with Flask.


You should continue to work in the FlaskLab folder that you made for the Flask intro lab. If you don’t have access to it anymore, just go through the steps to set up a basic Flask app with the dataset.csv file again.


As you know from your reading, Flask allows you to connect with HTML templates. Flask handles finding these as long as you put them where it is expecting.

(Fun fact/note: because I’m using a framework that has very similar syntax to Jinja to make this website, I have to do a special escape to actually display all the {{var}} , and I might have missed a few, so if you see a strangely blank spot, it is very likely that it should have some curly braces with a variable in it.)

  1. Create a templates folder in your FlaskLab folder
  2. Create a file in that folder index.html and put in the following boilerplate:
  3. Within the heading put in a set of title HTML tags and place a placeholder {{title}} between them:
  4. If you have as many tabs open as I do regularly, you can’t actual see the titles easily, so, within the body, put in a heading with the title as well:
     <h1>Welcome to the {{title}}!</h1>
  5. Now you need to go edit your existing Flask app to use your new template. Open flask_lab_app.py and edit your homepage() function so that instead of just returning a plain string, it returns the result of calling render_template with your title of choice:
     def homepage():
         return render_template('index.html', title="Silly Dataset")
  6. Run your app and check out your new fancy (kind of) homepage!

Data with Templates

Even though you don’t strictly have to use Jinja, it makes displaying lists much easier. Let’s display the headings of the silly dataset on the homepage.

  1. Within index.html make an unordered list in the body:
  2. Within that unordered list, we’ll use Jinja to make a list item for each heading in our list headings:
     {% for heading in headings: %}
     <li>{{ heading }}</li>
     {% endfor %}
  3. Now we need to actually pass that argument. Within flask_lab_app.py, add to the arguments that you are passing to render_template in homepage:
     def homepage():
         return render_template('index.html', title="Silly Dataset", headings = data[0])
  4. Restart your app to see your new fancy list!
  5. Try adding another list of the first data row of the silly dataset.

Fun extra

By combining the route variables and Jinja placeholders, you can let the user display what they want on your page. Try making a new template and route so that you can go to your_url/greeting/your_name and find a web page that greets whatever the user puts for your_name.

Applying to your project

You don’t need to use HTML templates for what you submit tonight and Monday, but you will need them for the team project eventually, so it’s a good idea to try adding one to your individual deliverable project for practice.

Otherwise, feel free to keep working on your individual deliverable Flask app and/or your team’s Flask app.