Python output highlighting in Quarto

Question

Continuing on this question about code output highlighting in Quarto: Is it also possible to make this work with Python output?

A minimal working example:

---
title: "Output line highlighting"
format: revealjs
editor: visual
filters:
  - output-line-highlight.lua
---

## Regression Table 

In R:

```{r}
#| class-output: highlight
#| output-line-numbers: "9,10,11,12"
LM <- lm(Sepal.Length ~ Sepal.Width, data = iris)
summary(LM)
```

## Regression Table

In Python:

```{python}
#| class-output: highlight
#| output-line-numbers: "12,13,14,15,16,17"
import pandas as pd
import statsmodels.api as sm

iris = sm.datasets.get_rdataset('iris').data
LM = sm.OLS(iris['Sepal.Length'], sm.add_constant(iris['Sepal.Width'])).fit()
LM.summary2()
```

Rendering this file shows the Lua filter works for the R output, but not for Python.

Answer 1

python code chunk doesn't support the chunk option output-class. Instead, use the option classes and use the class output-highlight. And for r-code chunk, you may use either class-output: highlight or classes: output-highlight.

And I have updated the filter to support the classes: output-highlight accordingly.

output-line-highlight.lua

function highlight(line_number)
  local highlighter = {
    CodeBlock = function(block)
      if block.classes:includes('highlight') then
        block.classes:insert('has-line-highlights')
        block.attributes["code-line-numbers"] = line_number
        return block
      end
  end
  }
  return highlighter
end

function add_highlight_class()
  return {
    CodeBlock = function(cb)
      if not cb.classes:includes('highlight') then
        cb.classes:insert('highlight')
      end
      return cb
    end
  }
end


function add_class_to_cb()
  return {
    Div = function(el)
      if el.classes:includes('cell-output') then
        return el:walk(add_highlight_class())
      end
    end
  }
end

function highlight_output_div()
  return {
    Div = function(div)
      if div.classes:includes('output-highlight') then
        return div:walk(add_class_to_cb())
      end
    end  
  }
end

function add_output_lnum()
  return {
    Div = function(el)
      if el.classes:includes('cell') then
        line_number = tostring(el.attributes["output-line-numbers"])
        return el:walk(highlight(line_number))
      end
    end
  }
end

function Pandoc(doc)
  if FORMAT == 'revealjs' then
    local doc = doc:walk(highlight_output_div())
    return doc:walk(add_output_lnum())
  end
end

presentation.qmd

---
title: "Output line highlighting"
format: revealjs
filters:
  - output-line-highlight.lua
---

## Regression Table 

In R:

```{r}
#| class-output: highlight
#| output-line-numbers: "9,10,11,12"
LM <- lm(Sepal.Length ~ Sepal.Width, data = iris)
summary(LM)
```

## Regression Table

In Python:

```{python}
#| classes: output-highlight
#| output-line-numbers: "2,4"

test = [1, 2, 3, 4]

for i in test:
  if i%2 == 0:
    print("this line is highlighted")
  else:
    print("this line is not highlighted")
```

---