Wow LaMouche, this is sweet Python code. I learned a lot about file reading/writing too. Here is what I have, showing it with my test file:
file sentences.txt looks like that:
Tom ate his Apple.
Frank shoveled Snow.
Henry drove a Truck.
f_in = open("sentences.txt","r")
lines = f_in.readlines()
lines_new = 
for line in lines:
lines_new.append(line.upper() + line[1:].lower())
f_out = open("sentences_fixed.txt", "w")
for line in lines_new:
file sentences_fixed.txt looks like that:
Tom ate his apple.
Frank shoveled snow.
Henry drove a truck.
My actual sentence file works fine too. I think I understand your code. Each line is a sentence and line.upper() simply makes certain that the first letter in the sentence is capitalized. To this you concatenate with the + the remainder of the sentence converted to lower case. Nice example of string slicing!