python - python中for循环的问题

Question

这段代码应该能够根据 self.order 中字符的顺序对 self.array 中的项目进行排序。方法 sort 会正常运行直到第三次迭代，除非由于某种原因 for 循环似乎无限重复。这是怎么回事？

编辑:我正在制作自己的排序函数，因为它是我的 python 作业的额外部分。

class sorting_class:
    def __init__(self):
        self.array = ['ca', 'bd', 'ac', 'ab'] #An array of strings
        self.arrayt = []
        self.globali = 0
        self.globalii = 0
        self.order = ['a', 'b', 'c', 'd'] #Order of characters
        self.orderi = 0
        self.carry = []
        self.leave = []
        self.sortedlist = []
    def sort(self):
        for arrayi in self.arrayt:  #This should only loop for the number items in self.arrayt. However, the third time this is run it seems to loop indefinitely. 
            print ('run', arrayi)   #Shows the problem
            if self.order[self.orderi] == arrayi[self.globali]:
                self.carry.append(arrayi)
            else:
                if self.globali != 0:
                    self.leave.append(arrayi)
    def srt(self):
        self.arrayt = self.array
        my.sort() #First this runs the first time.
        while len(self.sortedlist) != len(self.array):
            if len(self.carry) == 1:
                self.sortedlist.append(self.carry)
                self.arrayt = self.leave
                self.leave = []
                self.carry = []
                self.globali = 1
                self.orderi = 0
                my.sort()
            elif len(self.carry) == 0:
                if len(self.leave) != 0: #Because nothing matches 'aa' during the second iteration, this code runs the third time"
                    self.arrayt = self.leave
                    self.globali = 1
                    self.orderi += 1
                    my.sort()
                else:
                    self.arrayt = self.array
                    self.globalii += 1
                    self.orderi = self.globalii
                    self.globali = 0
                    my.sort()
                    self.orderi = 0
            else: #This is what runs the second time.
                self.arrayt = self.carry
                self.carry = []
                self.globali += 1
                my.sort()
my = sorting_class()  
my.srt()

Answer 1

Alex 提到的 key 提取器足够简单，可以放入 lambda 函数

>>> array = ['ca', 'bd', 'ac', 'ab']
>>> order = ['a', 'b', 'c', 'd']
>>> sorted(array, key=lambda v:map(order.index,v))
['ab', 'ac', 'bd', 'ca']

>>> order = ['b', 'a', 'c', 'd']
>>> sorted(array, key=lambda v:map(order.index,v))
['bd', 'ab', 'ac', 'ca']

>>> order = ['d', 'c', 'b', 'a']
>>> sorted(array, key=lambda v:map(order.index,v))
['ca', 'bd', 'ac', 'ab']

让我们看看它是如何工作的:

map 为 v 中的每个项目调用 order.index 方法，并使用这些返回值创建列表。
v 将是 array

的元素之一

>>> order = ['a', 'b', 'c', 'd']
>>> map(order.index,array[0])
[2, 0]
>>> map(order.index,array[1])
[1, 3]
>>> map(order.index,array[2])
[0, 2]
>>> map(order.index,array[3])
[0, 1]

该函数作为 key= 提供进行排序，因此在内部对这些列表而不是字符串进行排序。