Question

为什么第一个“标题”列表不起作用而第二个起作用？我如何使第一个工作？谢谢！

highlighted_poems = "Afterimages:Audre Lorde:1997,  The Shadow:William Carlos Williams:1915, Ecstasy:Gabriela Mistral:1925,   Georgia Dusk:Jean Toomer:1923,   Parting Before Daybreak:An Qi:2014, The Untold Want:Walt Whitman:1871, Mr. Grumpledump's Song:Shel Silverstein:2004, Angel Sound Mexico City:Carmen Boullosa:2013, In Love:Kamala Suraiyya:1965, Dream Variations:Langston Hughes:1994, Dreamwood:Adrienne Rich:1987"

highlighted_poems_list = highlighted_poems.split(',')

highlighted_poems_stripped = [line.strip() for line in highlighted_poems_list]

highlighted_poems_details = [line.split(':') for line in highlighted_poems_stripped]
print(highlighted_poems_details)

print()
print()
print()
print(highlighted_poems_details[1][1])

titles = [titles.append(title[0]) for title[0] in highlighted_poems_details]
#poets = [poet[1].append() for poet in highlighted_poems_details]
#dates = [date[2].append() for date in highlighted_poems_details]

for title in highlighted_poems_details:
  titles.append(title[0])
print(titles)

Answer 1

正确：

titles = [title[0] for title in highlighted_poems_details]

您没有在理解列表中添加任何内容，而是在定义它。

Answer 2

使用列表推导时，您必须先在for之后读取表达式，然后再读取第一部分：

titles = [title[0] for title in highlighted_poems_details]
          ^------^     ^--------------------------------^
              |                            |
       the information              iteration over 
       you want to add              your data
       to your new list

所以您可以这样阅读：for every title in the poem details, add title[0] to the list

Answer 3

或使用：

from operator import itemgetter
titles = list(map(itemgetter(0), highlighted_poems_details))

Answer 4

为什么不起作用？因为您在使用title时使用的是未定义变量title[0]，请参见下面的标记

titles = [titles.append(title[0]) for title[0] in highlighted_poems_details]
------------------------^^^^^^^-------^^^^^^^------------------------------

您可以按照Relandom的建议使用

titles = [title[0] for title in highlighted_poems_details]

转换一个简单的循环以列出理解

4 个答案: