python列表似乎随机消失

Question

我制作了一个脚本来测试我编写的不同排序算法的运行时间。代码在这里:

import random
import sort
import time

print ('test sort functions for integer lists')
integers = [random.randint(1,999) for n in range(1, random.randint(1000,2000)) ]
print('ordering', len(integers), 'ints')

print('start selection sort')
ts=time.clock()
print(sort.selection(integers))
print ('end selection sort with time', time.clock()-ts, '\n')


print('start merge sort')
tm=time.clock()
print(sort.merge(integers))
print ('end merge sort with time', time.clock()-tm, '\n')

当调用函数sort.merge(integers)时，由于某种原因，一个空列表被传递给它。我通过将 print(integers) 放在那里来测试这一点，但据我所知，应该与传递给 sort.selection(integers) 的列表完全相同。有人知道发生了什么事吗？

<小时/>

我的 sort.py 模块的内容:

import math

def merge(ints):
    if (len(ints) < 2):
        return (ints)
    else:
        print('recursion')
        i=merge(ints[0:math.ceil(len(ints)/2)]) #calls recursive function for
        j=merge(ints[math.ceil(len(ints)/2):])  #both halves of list
        k=[] #beginning of merge algorithm
        ic=0
        jc=0
        while (ic < len(i) and jc < len(j)):   #repeat as long as end of i
            if (i[ic] < j[jc]): #append lowest value to k
                k.append(i[ic])
                ic+=1 #track which values of i are accounted for
                if (ic == len(i)): #if i is exhausted
                    for a in range (jc, len(j)): #fill k with j
                        k.append(j[jc])
                        jc+=1
                    break
            if (i[ic] >= j[jc]):
                k.append(j[jc])
                jc+=1
                if (jc == len(j)):
                    for a in range (ic, len(i)):
                        k.append(i[ic])
                        ic+=1
                    break
        return (k) 

def selection(ints,order='a'):
    maxint=0
    orderedints=[]
    if (order == 'desc' or order == 'descending' or order == 'd'):
        while (len(ints) > 0):
            maxint=maxof(ints)
            ints.remove(maxint)
            orderedints.append(maxint)
        return (orderedints)

    if (order == 'asc' or order == 'ascending' or order == 'a'):
        while (len(ints) > 0):
            minint=maxof(ints)
            for i in range (0, len(ints)):
                if (ints[i] < minint):
                    minint = ints[i]
            ints.remove(minint)
            orderedints.append(minint)
        return (orderedints)

def maxof(a):
    maxint=0
    for i in range (0, len(a)):
        if (a[i] > maxint):
            maxint = a[i]
    return (maxint)

Answer 1

您的函数 sort.selection 正在修改传入的列表，如下所示:

ints.remove(maxint)

如果您想操作列表的本地副本，请添加:

ints = ints[:]

在 sort.selection() 例程的早期。