You could have done

    flights[['year', 'month', 'day']].head(10)

which is not so different from standard R

    head(flights[c("year", "month", "day")], 10)

but it's true that the following may be nicer

    flights[1:10, c("year", "month", "day")]

(by the way using head(10) is not the same as indexing 1:10 if there are less than 10 rows)