Can somebody write this program in python and comment on what is happening during each step, thank you in advance.

converts all words to lowercase, and prints out all words in the file that begin with that key letter a, the letter b, and so on. Build a dictionary whose keys are the lowercase letters, and whose values are sets of words which begin with that key letter. After processing the data, print the dictionary to the screen in alphabetical order aligned in two fixed sized columns. Do not add duplicate words to the dictionary. Such as:

a - {'add', 'alpha', 'at'}

b - {'both', 'but', 'box'}