Python looping through lists

Question

I have a list called:

word_list_pet_image = [['beagle', '01125.jpg'], ['saint', 'bernard', '08010.jpg']]

There is more data in this list but I kept it short. I am trying to iterate through this list and check to see if the word is only alphabetical characters if this is true append the word to a new list called

pet_labels = []

So far I have:

word_list_pet_image = []
for word in low_pet_image:
    word_list_pet_image.append(word.split("_"))

for word in word_list_pet_image:
    if word.isalpha():
        pet_labels.append(word)
        print(pet_labels)

For example I am trying to put the word beagle into the list pet_labels, but skip 01125.jpg . see below.

pet_labels = ['beagles', 'Saint Bernard']

I am getting a atributeError

AtributeError: 'list' object has no attribute 'isalpha'

I am sure it has to do with me not iterating through the list properly.

Answer 1

It looks like you are trying to join alphabetical words in each sublist. A list comprehension would be effective here.

word_list = [['beagle', '01125.jpg'], ['saint', 'bernard', '08010.jpg']]

pet_labels = [' '.join(w for w in l if w.isalpha()) for l in word_list]

>>> ['beagle', 'saint bernard']

Answer 2

You have lists of lists, so the brute force method would be to nest loops. like:

for pair in word_list_pet_image:
    for word in pair:
        if word.isalpha():
            #append to list

Another option might be single for loop, but then slicing it:

for word in word_list_pet_image:
    if word[0].isalpha():
        #append to list

Answer 3

word_list = [['beagle', '01125.jpg'], ['saint', 'bernard', '08010.jpg']]

---

为什么不list comprehension （只有非所有字母字母元素总是在最后）：

pet_labels = [' '.join(l[:-1]) for l in word_list]

Answer 4

word_list_pet_image.append(word.split("_"))

.split()返回列表，因此word_list_pet_image本身包含列表，而不是简单的单词。