source = ColumnDataSource(x)
bar = Bar(x, label='year', values='sales', agg='sum', stack='category',
    title='Expected Sales by year', tools='hover')
hover = bar.select(dict(type=HoverTool))
hover.tooltips = [('Year', '@x'), ('Sales', '@y')]
show(bar)
Data tooltips in Bokeh don't show data, showing '???' instead