This is the fourth option. Similarly to those options we've already looked at, we can use the right join to get a list of all the students who appeared in the Machine Learning course.

The code for doing it is as follows:

dfSE = pd.concat([df1SE, df2SE], ignore_index=True)
dfML = pd.concat([df1ML, df2ML], ignore_index=True)

df = dfSE.merge(dfML, how='right')
df

The output of this snippet is left as part of an exercise for you to complete. Check which columns have NaN values.