Enable line numbers to show on code cells.

[jwayne2978]

Is your feature request related to a problem? Please describe.

No

Describe the solution you'd like

When code cells are rendered, there should be a way to show line numbers. This could be done with tags. Narrating code requires precision with references to line numbers.

Describe alternatives you've considered

None.

Additional context

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[michaelosthege]

Inspired by readthedocs/sphinx_rtd_theme#1168 this worked for me in both HTML and pdflatex output:

```{code-block} python
---
name: code_linenumbers
linenos: True
caption: |
    This code has line numbers.
---
print("Hello")
print("world.")
```

Duplicate issue #1580

[chrisjsewell]

This was added in executablebooks/MyST-NB#380, available as nb_number_source_lines globally, and also per notebook or per code cell, see also https://myst-nb.readthedocs.io/en/latest/use/formatting_outputs.html#images-and-figures

[michaelosthege]

@chrisjsewell thanks for that context. Can you post/link an example of where the nb_number_source_lines setting should be set?

[chrisjsewell]

heya, its not released to jupyter-book just yet (only just merged that PR last week), in sphinx its just in the conf.py

[gao-hongnan]

Any updates pertaining to enabling line numbers to be shown on code blocks? Thanks!

[pierrepo]

This feature would allow me to mention specific code line in my course.

[michaelosthege]

This feature would allow me to mention specific code line in my course.

@pierrepo See #1254 (comment). This worked just fine for my thesis

[pierrepo]

Hello @michaelosthege

Thanks for your comment. I did not think it would work out of the box... and it did 🤯

So I have now to replace all:

```python

by

```{code-block} python
---
linenos: True
---

in my course. Many thanks for your help @michaelosthege 🙏

@chrisjsewell I still believe that a global code line numbering option would be useful in Jupyter Book.