如何在Python中按降序排序数字？

Question

我有以下这段代码，我想把金属的值按从大到小的顺序排列。我可以通过金属的名字来调用它们的每个数值，也就是我给它们起的名字。例如，如果我想调用铂金的值，我可以用“platinum.valuePerBar”。注意，我有一个自己的对象，叫做RIT_object，我可以在这个类里定义每个参数的类型，正如你在代码中看到的那样。

from rit_object import *            # rit_object class

class Metal(rit_object):
    """
    Represents a single metal type, composed of:
    :slot name (str): The name of the metal
    :slot totalBars (int): The total number of bars
    :slot weightPerBar (int): The weight of a single bar
    :slot valuePerBar (int): The value of a single bar
    :slot valuePerWeight (float): The value per weight of the metal
    :slot barsTaken (int): The number of bars added to the satchel
    """

    __slots__ = ( 'name' ,  'totalBars' , 'valuePerBar' , 'weightPerBar' , 'barsTaken' )
    _types = ( str , int , int, int, float, int )




def createMetal(name, totalBars, weightPerBar, valuePerBar):
    """
    Create and return a new Metal object.
    :param name (str): The name of the metal
    :param totalBars (int): The total number of bars
    :param weightPerBar (int): The weight of a single bar
    :param valuePerBar (int): The value of a single bar
    :return: A newly initialized Metal object
    :rtype: Metal
    """
    platinum = Metal("platinum", 1, 1000, 6, 0)
    gold = Metal("gold", 1, 750, 5, 0)
    rhodium = Metal("rhodium", 1, 500, 5, 0)
    silver = Metal("silver", 1, 400, 4, 0)

def sortMetalsByValuePerBar(metals):
    """
    Sort the metals by value per bar using insertion sort.  The list of
    metals is modified in place to be ordered by value per bar.
    :param metals (list of Metal): The list of metals
    :return: None
    :rtype: NoneType
    """

那么我该如何把这些值按从大到小的顺序排列呢？

Answer 1

试试使用 sorted 函数，并加上 reverse 参数。

sorted([1,2,3,4], reverse=True)

和你的代码有关：

来自 collections 模块的 namedtuple

Metal = namedtuple('Metal', 'name, totalBars, weightPerBar, valuePerBar')

platinum = Metal("platinum", 1, 1000, 100.23) 
gold = Metal("gold", 1, 750, 20.043) 
rhodium = Metal("rhodium", 1, 500, 10.93) 
silver = Metal("silver", 1, 400, 15.73)

metals = [platinum, silver, gold, rhodium]

# Sort by value in descending order
metals = sorted(metals, key=lambda x:x.valuePerBar, reverse=True)

for i in metals:
    print i.name, i.valuePerBar

[输出]:

platinum 100.23
gold 20.043
silver 15.73
rhodium 10.93