Question

下面的函数从URL的文本文件返回单词列表：

def fetch_words():
    with urlopen('http://sixty-north.com/c/t.txt') as story:
        story_words = []
        for line in story:
            line_words = line.decode('utf-8').split()
            for word in line_words:
                story_words.append(word)
    return story_words

我很想看看是否可以将其转换为等效的列表理解方法。我尝试过：

with urlopen('http://sixty-north.com/c/t.txt') as story:
     return [word for word in line.decode('utf-8').split() 
             for line in story]

，但出现“未解析的参考'行'”错误。看来我误会了嵌套列表理解的工作原理，有人可以解释吗？

Answer 1

您的语法略有错误，请尝试以下操作：

return [word for line in story for word in line.decode('utf-8').split()]

Answer 2

当列表理解有两个循环时，它们的顺序必须与语句的顺序相同：

with urlopen('http://sixty-north.com/c/t.txt') as story:
    return [
        word 
        for line in story
        for word in line.decode('utf-8').split() 
    ]

Answer 3

为简单起见，我建议使用requests模块：

<question-host *ngFor="let question of questions" [question]="question" hidden></question-host>

不需要上下文管理器。

如果您要读取的数据很小，则可以使用

story_words = [
    word 
    for line in requests.get('http://sixty-north.com/c/t.txt').iter_lines() 
    for word in line.decode('utf-8').split()
]

可以将其转换为列表理解吗？

3 个答案: