data = [k.split() for k in
    """2016    A           1
2016    B           1
2016    C           1.5
2017    A           2
2017    B           3
2017    C           1
2018    A           2.5
2018    B           3
2018    C           2"""
    .split('\n')]
x = pd.DataFrame(data, columns=['year', 'category', 'sales'])
x['year'] = x['year'].astype(object)
x['sales'] = x['sales'].astype(float)
Data tooltips in Bokeh don't show data, showing '???' instead