Groupby sum of col1 divided by sum of col2

Question

I have DF like this:

and I want to calculate how much is students was prepared via his overall score in the exam, like this:

How can I do it?

Answer 1

You probably want something like this:

s = df.groupby(['Student', 'Exam']).apply(lambda group: (f'{group["IsCorrect"].sum()}\\{group.shape[0]}', (group['IsCorrect'].sum() / group.shape[0]))).reset_index(drop=True)
df['prepared'] = s.str[0]
df['prepared percentage'] = s.str[1]