在python中有一个对象数组，如何通过属性对其元素进行分类？

Question

在Python中，是否有一个函数可以通过属性对对象数组进行分类和排序？

示例：

class Book:
    """A Book class"""
    def __init__(self,name,author,year):
        self.name = name
        self.author = author
        self.year = year

hp1 = Book("Harry Potter and the Philosopher's stone","J.k Rowling",1997)
hp2 = Book("Harry Potter and the chamber of secretse","J.k Rowling",1998)
hp3 = Book("Harry Potter and the Prisioner of Azkaban","J.k Rowling",1999)

#asoiaf stands for A Song of Ice and Fire
asoiaf1 = Book("A Game of Thrones","George R.R Martin",1996)
asoiaf2 = Book("A Clash of Kings","George R.R Martin",1998)

hg1 = Book("The Hunger Games","Suzanne Collins",2008)
hg2 = Book("Catching Fire","Suzanne Collins",2009)
hg3 = Book("Mockingjaye","Suzanne Collins",2010);

books = [hp3,asoiaf1,hp1,hg1,hg2,hp2,asoiaf2,hg3]
#disordered on purpose

organized_by_autor = magic_organize_function(books,"author")

magic_organize_function是否存在？否则，会是什么？

Answer 1

按作者排序是一种方式：

sorted_by_author = sorted(books, key=lambda x: x.author)
for book in sorted_by_author:
    print(book.author)

输出：

George R.R Martin
George R.R Martin
J.k Rowling
J.k Rowling
J.k Rowling
Suzanne Collins
Suzanne Collins
Suzanne Collins

您还可以使用itertools.groupby很好地按作者分组：

from itertools import groupby

organized_by_author = groupby(sorted_by_author, key=lambda x: x.author)

for author, book_from_author in organized_by_author:
    print(author)
    for book in book_from_author:
        print('    ', book.name)

输出：

George R.R Martin
     A Game of Thrones
     A Clash of Kings
J.k Rowling
     Harry Potter and the Prisioner of Azkaban
     Harry Potter and the Philosopher's stone
     Harry Potter and the chamber of secretse
Suzanne Collins
     The Hunger Games
     Catching Fire
     Mockingjaye

注意：您需要向排序groupby提供sorted_by_author。