Escaping special chars in col names with a single backslash raises warnings

[joelostblom]

What happened?

When I run the example with special chracters from the docs, I see a bunch of warnings:

What would you like to happen instead?

Replacing the single \ with double \\ fixes the issue. We could just update the docs, but before doing so I'm curious if anyone knows if something changed (in altair/ipython/python) that makes this warning visible now and if others see it or it is something with my local env.

Which version of Altair are you using?

main

[jonmmease]

Rather than using double backslashes, I think using raw strings (those prefixed by r, e.g. r'col\.period') would fix the issue by bypassing Pythons own escaping logic. And I think this makes things a little easier to reason about.