如何对元组进行排序

Question

我想知道如何按字母顺序排列元组。

cities_countries=[('doha','qatar'),('ankara','turkey'),('rome','italy'),('brussels','belgium')] 

的结果应该是：

belgium, brussels 
italy, rome 
qatar, doha 
turkey,ankara 

如果可能的话，我可以使用循环

Answer 1

您可以在同一行做到这一点使用内置的排序

cities_countries=[('doha','qatar'),('ankara','turkey'),('rome','italy'),('brussels','belgium')] 

sorted(cities_countries, key=lambda x: x[1]) 
# [('brussels', 'belgium'), 
# ('rome', 'italy'), 
# ('doha', 'qatar'), 
# ('ankara', 'turkey')] 

# and to get it in the order you want 
map(lambda x: (x[1], x[0]), sorted(cities_countries, key=lambda x: x[1])) 

# [('belgium', 'brussels'), 
# ('italy', 'rome'), 
# ('qatar', 'doha'), 
# ('turkey', 'ankara')]