# Exercise 16: Custom cell tags

With the extended functionality of live code, additional cell tags have been developed that can be added to Python code cells in any `.ipynb` file. These tags extend the [existing Jupyter Book tags](https://jupyterbook.org/en/stable/content/metadata.html) and allow you to control how cells behave when live execution is enabled.

::::::{topic} Exercise objective
Can you apply custom cell tags to control the execution and visibility of code cells?
::::::

## Available custom tags

- `disable-execution-cell` disables the ability to execute the cell when live code is activated. This is useful if your notebook includes interactivity for only part of the cells.  
- `disable-execution-page` disables the ability to execute the entire page. This can be helpful if Python code is used to build a page but is not meant to be run by readers.  
- `auto-execute-page` automatically starts live coding when the page is opened, useful if you are using widgets.  
- `thebe-init` runs this cell automatically as soon as live coding starts.  
- `thebe-remove-input-init` is similar to `thebe-init` but hides the input from students while still executing it. (The regular `remove-input` tag will not work here, since it deletes the entire cell.)  

```{tip}
Tags are case-sensitive. Use lowercase and match them exactly as shown above.
````


## Creating a notebook

1. In your repository, create a new notebook file in your book directory, e.g. `book/live_code_tags.ipynb`.
2. Add a new code cell with something simple inside, for example:

```python
print("Hello from live code!")
```

3. When you are ready, commit your changes to the repository by clicking on the green `Commit changes` button.

4. Add a commit message.

5. To see your changes, go to {octicon}`play` `Actions` - The most recent workflow run `overview.md / the commit message of the commit you just made` - Wait for it to finish - In the summary, click on the link of your book shown in the table `Branches deployed` and under `Primary book at root` (getting bored of waiting? There'll be exercising on doing this locally which prevents you from waiting).

6. Do you see your change? If you don't see it click `CTRL`+`F5`/`Control`+`F5`to refresh the page.

## `disable-execution-cell`

7. Now let's go back to your notebook. Open the cell metadata (in JupyterLab or Jupyter Notebook: `View → Cell Toolbar → Tags`).
8. Add the tag `disable-execution-cell` to your code cell, and commit and rebuild your book.
9. Visit the page — notice that this particular cell can no longer be run when live code is activated.

## `disable-execution-page`

10. Add another code cell to your file, for example:

```python
print("Goodbye from live code!")
```
11. Add the tag `disable-execution-page` to any of the live cell codes in your file, and commit and rebuild your book.
12. Visit the page — none of the cells should be executable now.

```{note}
Remove this tag again before continuing, otherwise the next tags won’t have any effect.
```

## `auto-execute-page`

13. Add the tag `auto-execute-page` to any cell and rebuild your book.
14. Visit the page — live code should automatically start running without clicking the “launch” button.

## `thebe-init`

15. Add the tag `thebe-init` to any cell and rebuild your book.
16. Visit the page — as soon as live code starts, this cell will run by itself.

## `thebe-remove-input-init`

17. Replace the previous tag with `thebe-remove-input-init`, and rebuild your book.
18. Visit the page — you should only see the **output** of the cell, not the code, but the cell is still executed automatically when live code starts.




```{admonition} Check your understanding
:class: note

Before moving on, make sure you understand the following:
- How do you add tags to a cell in an `.ipynb` file?  
- Which tag disables execution for a single cell? For the whole page?  
- Which tag makes a page auto-start live code when opened?  
- What is the difference between `thebe-init` and `thebe-remove-input-init`?  
```