Add raw_html parameter to Styler.format, enabling richer output

[jnothman]

Styler.format could allow a parameter raw_html (bool, False for current behaviour), enabling richer output

For example, df.style.format(lambda s: f"<a href='https://en.wikipedia.org/wiki/{html.escape(s)}'>{html.escape(s)}</a>", raw_html=True) could be used to turn a column of values into a column of links to English Wikipedia articles, when exported with to_html.

To achieve this, we would need to always pass raw HTML to the jina templates, changing how formatting is currently done in Styler.to_html.

Formats performed with raw_html=True would have no effect on Styler.to_excel.

[attack68]

does using jinja2 safe keyword help here? {{ something.render() | safe }}? maybe that is an easy fix? maybe not..

[jnothman]

The jinja2 safe keyword would be necessary for this feature to work. But complementary functionally in pandas to distinguish between safe and unsafe formats would be necessary

[attack68]

@jnothman, OK ignore my comment I misunderstood I think I now understand what you are trying to achieve, correct me if I am wrong, but of the following:

from jinja2.filters import escape
df = pd.DataFrame([["just&'beans'", 'Fish<div>Chips']])
format_func_1 = lambda v: f'<a href="https://www.abc.com/{v}">{v}</a>'
format_func_2 = lambda v: f'<a href="https://www.abc.com/{escape(v)}">{v}</a>'
format_func_3 = lambda v: escape(f'<a href="https://www.abc.com/{v}">{v}</a>')
format_func_4 = lambda v: f'<a href="https://www.abc.com/{escape(v)}">{escape(v)}</a>'
df.style.format(format_func_x).render()

Will only render correctly in the final case. So basically it eliminates no-escaping (case 1), selective display value escaping (case 2) and post-formatting escaping (case 3). We need to escape the display value before the formatter acts on it.

i.e. format(lambda v: f'<a href="https://www.abc.com/{v}">{v}</a>', escape=True) should act as case 4.

[jnothman]

yes, it seems as though I was mistaken about the current behaviour. I had thought it would already escape the content for me. I had presumed so just because of the use of jinja templates. Now I need to go back and look at where in my code I'd thought I'd needed this!

In the context of my confusion, your PR seems appropriate @attack68!