列出python中的切片问题

Question

This code seems like it should work. It sums up the number of words that are "striped" (letter-consonant-letter-etc.) and then returns the sum. However when I test it with print (striped("My name is ...") ) it only counts my and is and gives me a sum of 2 instead of 3... why is name missing?

VOWELS = "AEIOUY"
CONSONANTS = "BCDFGHJKLMNPQRSTVWXZ"


def striped(text):

    my_sum = 0
    text = text.replace(".", " ").replace(",", " ").split()
    vowels = VOWELS.lower()
    consonants = CONSONANTS.lower()

    for word in text:
        word = word.lower()
        if ((word[::2] in vowels and word[1::2] in consonants)\
        or (word[::2] in consonants and word[1::2] in vowels))\
        and len(word) > 1:
            print (word)
            my_sum += 1

    return my_sum        

Answer 1

You should use set.issubset() instead.

VOWELS = "AEIOUY"
CONSONANTS = "BCDFGHJKLMNPQRSTVWXZ"

def striped(text):

    my_sum = 0
    text = text.replace(".", " ").replace(",", " ").split()
    vowels = set(c for c in VOWELS.lower())
    consonants = set(c for c in CONSONANTS.lower())

    for word in text:
        word = word.lower()
        if ((set(word[::2]).issubset(vowels) and set(word[1::2]).issubset(consonants))\
        or (set(word[::2]).issubset(consonants) and set(word[1::2]).issubset(vowels)))\
        and len(word) > 1:
            print (word)
            my_sum += 1
    return my_sum        

striped('My name is...')

The reason it works for my and is is that they are two char words, so you are checking if if m is in the string of constants, and if y is in the string of vowels, which works. For longer words like name , then clearly nm is not in the string of sonsonants, so it fails.

---

Instead, you should use sets. Essentially, you want to find if set(['n','m']) is a subset of the set of consonants.

Answer 2

Here is a solution with lists. The problem with your code is that words longer than two characters return a substring when you use [::2] rather than single characters that are tested whether they are contained in vowels / constants . By converting it to a list first, you can check every item of the list whether it is contained in the according set of characters.

VOWELS = "AEIOUY"
CONSONANTS = "BCDFGHJKLMNPQRSTVWXZ"


def striped(text):

    my_sum = 0
    text = text.replace(".", " ").replace(",", " ").split()
    vowels = VOWELS.lower()
    consonants = CONSONANTS.lower()

    for word in text:
        word = word.lower()

        if ((all(c in vowels for c in list(word[::2]))\
            and all(c in consonants for c in list(word[1::2])))\
        or (all(c in consonants for c in list(word[::2]))\
            and all(c in vowels for c in list(word[1::2]))))\
        and len(word) > 1:
            print (word)
            my_sum += 1

    return my_sum

print striped("My name is")