with open('revisor.txt') as f:
    slova = set()
    for i in f:
        for j in i.lower().split():
            w = ''
            for k in j:
                if k.isalpha():
                    w += k
                else:
                    slova.add(w)
                    w = ''
            if w != '':
                slova.add(w)
slova.remove('')
slova = sorted(slova)
slova = sorted(slova, key=lambda x: len(x))
print(slova)