Question

所以我对Python很新，并且因为我的入门级CS课程而遇到问题。问题是创建一个列表，其中包含2000年之前创建的所有标题以及2000年之后创建的所有标题。这是我到目前为止所拥有的：

from collections import namedtuple
Book = namedtuple("Book", "author title genre year price instock")
book_1 = Book("Bob", "Harry Potter", "Fantasy", 2000, 6.00, 1000)
book_2 = Book("Martha", "Hunger Games", "Psychological", 1998, 10.00, 2000)
book_3 = Book("Sam", "The Quest", "Adventure", 2010, 8.00, 5000)
book_4 = Book("Damien", "Pokemon", "Sci-Fi", 1990, 12.00, 10000)
book_5 = Book("Voldemort", "Maze Runner", "Adventure", 2015, 10.00, 50)
book_6 = Book("Anonymous", "Horror Stories Before Bed", "Horror", 2017, 18.00,0)
book_store_inventory = [book_1, book_2, book_3, book_4, book_5, book_6]

before_2000 = []
after_2000 = []

for i in book_store_inventory:
    if book_store_inventory[i].year <= 2000:
        before_2000.append(i.title)
    else:
        after_2000.append(i.title)

从这一点开始，我应该改变什么？我不断收到错误消息，说列表索引必须是整数或切片，而不是Book。谢谢！

Answer 1

你不需要索引：

for book in book_store_inventory:
    if book.year <= 2000:
        before_2000.append(book.title)
    else:
        after_2000.append(book.title)

Answer 2

before_2000 = [i.title for i in book_store_inventory if i.year <= 2000]

after_2000 = [i.title for i in book_store_inventory if i.year > 2000]

Answer 3

由于您有这么多书籍对象，因此创建一个新类来存储书籍并创建property装饰器以根据特定条件访问库数据可能是有意义的：

class Library:
   def __init__(self, books):
      self.books = books
   @property
   def before_2000(self):
      return [i for i in self.books if i.year <= 2000] 
   @property
   def after_2000(self):
      return [i for i in self.books if i.year > 2000]
   def __repr__(self):
       return '{}({})'.format(self.__class__.__name__, ', '.join(i.title for i in self.books))

book_store_inventory = [book_1, book_2, book_3, book_4, book_5, book_6]
library = Library(book_store_inventory)
print(library.before_2000)
print(library.after_2000)
print(library)

输出：

[Book(author='Bob', title='Harry Potter', genre='Fantasy', year=2000, price=6.0, instock=1000), Book(author='Martha', title='Hunger Games', genre='Psychological', year=1998, price=10.0, instock=2000), Book(author='Damien', title='Pokemon', genre='Sci-Fi', year=1990, price=12.0, instock=10000)]
[Book(author='Sam', title='The Quest', genre='Adventure', year=2010, price=8.0, instock=5000), Book(author='Voldemort', title='Maze Runner', genre='Adventure', year=2015, price=10.0, instock=50), Book(author='Anonymous', title='Horror Stories Before Bed', genre='Horror', year=2017, price=18.0, instock=0)]
Library(Harry Potter, Hunger Games, The Quest, Pokemon, Maze Runner, Horror Stories Before Bed)

如何使用另一个namedtuples列表追加到列表？

3 个答案: