(4.a) Write a function numOccur(s), where s is a string; the function should return a dictionary whose keys are the 26 ascii letters abcdefghijklmnopqrstuvwxyz . At each key (i.e., for each one of these 26 ascii letter), the value should be the number of times this letter occurs in s. The string s can contain all kinds of ascii characters; only the letters should be counted, the rest should be ignored. Your function should read the string s just once.
(4.b) Find the returned dictionary when you run numOccur(s) on the string consisting of the entire content of the attached le DictFileSetHW. Make sure you save this le as a plain text- le (in the same way as you save your Python programs), in the same directory as your Python program.
Then in interactive python3, use Python le commands to open the le and copy it into one string s. Review the commands open(..,..), .read(), and .close() in the handout DictFileSet or DictFileSetHW.
Show (as commnents) the le commands you use and the resulting dictionary