counting and figuring out the average amount of words in a program

I have a program that should calculate the average amount of characters in a list of strings but it is not working.

#Program that calculates the average length of the items in a list of strings

#Ask the user to input the amount of strings that they want to enter
nofs= eval(input("Please enter the number of strings you want to enter: "))                 

#Prompt user for a sentence
for i in range(nofs):
    sentence= str(input("Please enter a sentence: "))

#Count the number of words
sentencesplitting= sentence.split(" ")

#Count the number of characters
charactercount= len(sentencesplitting)

#Find the average (number of characters divided by the number of words
average = (charactercount)/(sentencesplitting)

#Print the average


I do not understand how to get this program to work.