尝试使用itertools.permutations时出现MemoryError，如何使用较少的内存? [英] MemoryError while trying to using itertools.permutations, how use less memory?

问题描述

我正在从包含如此随机字符串的文本文档中加载文件，并且尝试打印该字符串中所有可能的字符排列.

I'm loading from a text document containing so random strings and I'm trying to print every possible permutation of the characters in that string.

如果记事本包含例如:

123
abc

我希望输出为

123,132,213,231,312,321
abc,acb,bac,bca,cab,cba

该文本文件包含一些相当大的字符串，因此我可以看到为什么收到此MemoryError.

The text file contains some pretty large strings so I can see why I am getting this MemoryError.

我第一次尝试使用它:

import sys
import itertools
import math

def organize(to_print):
    number_list = []
    upper_list = []
    lower_list = []
    for x in range(0,len(to_print)):
        if str(to_print[x]).isdigit() is True:
            number_list.append(to_print[x])
        elif to_print[x].isupper() is True:
            upper_list.append(to_print[x])
        else:
            lower_list.append(to_print[x])
    master_list = number_list + upper_list + lower_list
    return master_list

number = open(*file_dir*, 'r').readlines()

factorial = math.factorial(len(number))
complete_series = ''

for x in range(0,factorial):
    complete_string = ''.join((list(itertools.permutations(organize(number)))[x]))

    complete_series += complete_string+','
edit_series = complete_series[:-1]
print(edit_series)

def organize的原因是，如果我有一个字符串1aB，则在开始排列之前，我需要按数字，大写，小写对其进行排序.

The reason for def organize is if I have a string 1aB I would need to preorder it by number,uppercase,lowercase before I start the permutations.

我在这里遇到内存错误:complete_string = ''.join((list(itertools.permutations(organize(number)))[x]))，所以我最初的尝试是将其带出for循环.

I got the memory error here: complete_string = ''.join((list(itertools.permutations(organize(number)))[x])) so my initial attempt was to bring it out of the for-loop.

我的第二次尝试是

import sys
import itertools
import math

def organize(to_print):
    number_list = []
    upper_list = []
    lower_list = []
    for x in range(0,len(to_print)):
        if str(to_print[x]).isdigit() is True:
            number_list.append(to_print[x])
        elif to_print[x].isupper() is True:
            upper_list.append(to_print[x])
        else:
            lower_list.append(to_print[x])
    master_list = number_list + upper_list + lower_list
    return master_list

number = open(*file_dir*, 'r').readlines()

factorial = math.factorial(len(number))
complete_series = ''
the_permutation = list(itertools.permutations(organize(number)))

for x in range(0,factorial):
    complete_string = ''.join((the_permutation[x]))

    complete_series += complete_string+','
edit_series = complete_series[:-1]
print(edit_series)

但是我仍然遇到内存错误.我不一定需要或直接想要答案，因为这是减少我的低效率的良好学习习惯，因此朝正确方向的提示会很好.

But I am still getting a memory error. I don't necessarily need or want the answer directly as this is good learning practice to reduce my inefficiencies, so hints in the right direction would be nice.

添加了第三次尝试:

import sys
import itertools
import math

def organize(to_print):
    number_list = []
    upper_list = []
    lower_list = []
    for x in range(0,len(to_print)):
        if str(to_print[x]).isdigit() is True:
            number_list.append(to_print[x])
        elif to_print[x].isupper() is True:
            upper_list.append(to_print[x])
        else:
            lower_list.append(to_print[x])
    master_list = number_list + upper_list + lower_list
    return master_list

number = open(*file_dir*, 'r').readlines()

factorial = math.factorial(len(number))
complete_series = ''
the_permutation = itertools.permutations(organize(number))
for x in itertools.islice(the_permutation,factorial):
    complete_string = ''.join(next(the_permutation))
    complete_series += complete_string+','
edit_series = complete_series[:-1]
print(edit_series)

推荐答案

不调用列表，只需遍历排列即可:

Don't call list, just iterate over the permutations:

the_permutation = itertools.permutations(organize(number))

for x in the_permutation:
    complete_string = ''.join(the_permutation)

list(itertools.permutations(organize(number)))将所有排列存储在内存中，然后将所有排列存储在循环中的字符串中，即使使用此方法，也无法保证您将能够存储所有数据，具体取决于所存储的数据量the_permutation

list(itertools.permutations(organize(number))) stores all the permutations in memory then you store all the permutations in a string in your loop, there is no guarantee that you will be able to store all the data even using this approach depending on how much data is in the_permutation

如果只需要一定数量的置换，则可以在置换对象中调用下一个:

If you only want a certain amount of the permutations you can call next om the permutations object:

the_permutation = itertools.permutations(organize(number))
for x in range(factorial):
    complete_string = ''.join(next(the_permutation))

或使用itertools.islice:

Or use itertools.islice:

for x in itertools.islice(the_permutation,factorial):
    complete_string = ''.join(next(the_permutation))

这篇关于尝试使用itertools.permutations时出现MemoryError，如何使用较少的内存?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！