BUG: Clearing a `Styler` should clear all

[attack68]

Currently Styler.clear() will clear the styles built up with the apply aaplymap and where method. It will clear class from the set_td_classes method and it will clear tooltips set with set_tooltips.

It does not clear table styles, and it does not clear formats. It does not reset hidden index or hidden columns.

Thoughts and PR into what this should do and how it should it be documented, as well consistency with Styler.copy are welcome..

[bsun94]

hi there, I'm still new around here, but would like to help take on this issue. I'd love to help look into the issue more - would you mind pointing me to the relevant section of the code base to start taking a look?

[attack68]

All items relating to Styler are in pandas/io/formats/style.py - there you will find the discussed class methods.
Tests are in pandas/tests/io/formats/style/..

[bsun94]

thank you!

[bsun94]

I took a look at the module, I think changing the state of the self.hidden_index and self.hidden_columns attributes in the clear(), apply(), etc. methods is relatively straightforward - changing the values back to their __init__() defaults in the clear() and adding lambda expressions in the self._todo for the others.

Resetting the self.table_styles may depend - if we just want to "reset" it to an empty list every time, then that's also straightforward. But if we'd want to reset it back to whatever the user may have input into the __init__(), then we may need a second init variable to store that initial state, to refer back to. Which approach would be preferred here?

[attack68]

I think go with the most straight forward option initially, which is a good first step, and defer the decision about replicating the __init__ state until after, personally I probably just prefer clearing to default None, rather than back to the __init__ state.

I think clearing hidden_columns, hidden_index, _todo, ctx cell_context Tooltips and format table_styles back to (empty) default are all probably necessary

[bsun94]

Thanks attack, I've updated the clear to include _todo, hidden_index, hidden_columns and tooltips. Since both format and table_styles are dependant upon parameters that the user may input into the __init__, I've left those out for now. I'll try to write some tests for these as a next step before pushing.

As for #22851 referenced here, from what I can tell at least, exporting styles entirely rely on what's included in _todo, which is only executed in the _compute method. One solution I can think of is 1) append to _todo in each of the styling methods e.g. hide_index, but using a differently-lengthed tuple and 2) repurposing the for loop in _compute to use _apply and _applymap as it currently does if the _todo tuple in the current iteration has len = 3, else assume the tuple indicates an instance state change (from one of the above styling methods) and simply alter the value of the indicated instance variable.