BUG: Styler.apply and applymap duplicate CSS on re-render. #39395
Description
Code Sample, a copy-pastable example
df = pd.DataFrame((np.random.rand(1, 1)*100)) s = df.style\ .applymap(lambda x: 'background-color: black;')\ .apply(lambda x: pd.DataFrame([['color: red;']]), axis=None) print(s.render()) print(s.ctx) print(s.render()) print(s.ctx) ... <style type="text/css" > #T_fda50_row0_col0{ background-color: black; color: red; }</style> defaultdict(<class 'list'>, {(0, 0): ['background-color: black', 'color: red']}) <style type="text/css" > #T_fda50_row0_col0{ background-color: black; color: red; background-color: black; color: red; }</style> defaultdict(<class 'list'>, {(0, 0): ['background-color: black', 'color: red', 'background-color: black', 'color: red']})Problem description
The private _todo list is not cleared after initial execution so repeats the execution on second render.
There does not seem to be any reason any reason to maintain the _todo list after it has been done and the ctx object has been updated with necessary css-styles.
Expected Output
Same on each render.