def is_isogram(word):
    stripped = remove_punctuation(word)
    return len(stripped) == len(set(stripped))

def remove_punctuation(word):
    return filter(str.isalpha, word)

def is_isogram(word):
    return len(remove_punctuation(word)) == len(set(remove_punctuation(word)))

def remove_punctuation(word):
    return filter(str.isalpha, word.lower())

Solve isogram