import re
def findnum(filename):
    with open(filename, 'r') as fin,open('frequency.txt','w') as fout:
        text = fin.read()
        word = re.findall("[a-z]+",str.lower(text))
        word_set = list(set(word))
        word_set = sorted(word_set)
        print(word_set)
        for i in word_set:
            non_word = re.match("-+",i)
            if not non_word:
                fout.write(i +" : "+str(word.count(i))+"\n")
if __name__ == '__main__':
    findnum('a.txt')