Pandas Dataframe for duplicate values

Hello,

i have a very short query regarding pandas dataframe
my dataframe looks like


True Class, Predicted Class, Confi
800 750 0.67
800 800 0.42
800 750 0.32
800 750 0.98
800 900 0.34
800 900 0.45
. . .
. . .
. . .
800 750 0.77


i would like to add the percentages of repeated prediction class values and plot predicted class vs (added percentage per prediction class) so 900 = (0.34+0.45) and then 800 = 0.42 etc etc if you know what i mean.

im struggling to group by this data could you please help me with this creating these two arrays by any chance.