The original dataset is:

# (numbersofrating,title,avg_rating)
newRDD =[(3,'monster',4),(4,'minions 3D',5),....] 

I want to select top N avg_ratings in newRDD.I use the following code,it has an error.

selectnewRDD = (newRDD.map(x, key =lambda x: x[2]).sortBy(......))TypeError: map() takes no keyword arguments

The expected data should be:

# (numbersofrating,title,avg_rating)
selectnewRDD =[(4,'minions 3D',5),(3,'monster',4)....] 

You can use either top or takeOrdered with key argument:

newRDD.top(2, key=lambda x: x[2])

or

newRDD.takeOrdered(2, key=lambda x: -x[2])

Note that top is taking elements in descending order and takeOrdered in ascending so key function is different in both cases.