将我文件中每一行的第三个单词分配给 Python 中的列表

Question

I have a text file 'news.txt' , and I'm trying to save the third word of every line in a list(three) and I just keep getting a vector with the third word in the line over and over it doesn't seem to register the other words in the following lines.

with open('news.txt', 'r') as file:
    content = file.read()
    words = content.split() 
    for bwords in words:
        three = bwords[2]

Answer 1

with open('news.txt', 'r') as file:
    content = file.read()
    words = content.split()
    for bwords in words[::3]:
        three = bwords

Answer 2

You need to create a list before the for cycle and then append results to this list:

with open('news.txt', 'r') as file:
    content = file.read()
    words = content.split()
    three = [] 
    for bwords in words:
        three.append(bwords[2])

Otherwise you're just getting the third word from the last line the cycle ran through.

Alternatively, you can do it with a list comprehension:

three = [word[2] for word in words]

Answer 3

I'd create an iterator (using a generator comprehension) and then supply the iterator to a list.

Like so:

with open('news.txt', 'r') as file:
    # create the iterator using a generator comprehension
    iter_word_3 = (word_list[2] for word_list in 
                   (line.split() for line in file))
    # feed the iterator to the list function
    threes = list(iter_word_3)

Optionally you could create a generator function separately rather than using a generator comprehension. A nice thing about doing it this way is you can tell the program how to handle the IndexError if there isn't a 3rd word. You could even make it a utility function that accepts arguments:

def iter_xth_word(x, filestream):
    """Iterates over xth word from each line of a file."""
    for line in filestream:
        try:
            yield line.split()[x-1]
        except IndexError:
            # ignore lines without a xth word
            continue

with open('news.txt', 'r') as file:
    # create the iterator using a generator comprehension
    iter_word_3 = iter_xth_word(3, file)
    # feed the iterator to the list function
    threes = list(iter_word_3)