File contents

import string

def removeJunk(mystring):
	newstring = ''
	for char in mystring:
		if char in string.letters or char == ' ':
			newstring += char
	return newstring

def stringToWords(mystring):
	return mystring.split()

def removeUnwantedWords(mylist):
	unwanted = ['of', 'at', 'the', 'and']
	new_list = []
	for word in mylist:
		if word not in unwanted:
			new_list = new_list + [word]
	return new_list

def generateAcronym(mystring):
	if type(mystring) != str:
		return None
	filtered = removeJunk(mystring.lower())
	wordlist = stringToWords(filtered)
	wordlist = removeUnwantedWords(wordlist)
	if (len(wordlist) == 0):
		return None
	acronym = ''
	for word in wordlist:
		acronym += word[0].upper()
	return acronym