将数字字符串编码为缩短的字母数字字符串，然后再次返回 [英] Encoding a numeric string into a shortened alphanumeric string, and back again

问题描述

快速提问。我正在尝试在Python中查找或编写编码器，以通过使用大小写字母来缩短数字字符串。数字字符串看起来像这样：

Quick question. I'm trying to find or write an encoder in Python to shorten a string of numbers by using upper and lower case letters. The numeric strings look something like this:

20120425161608678259146181504021022591461815040210220120425161608667

长度始终相同。

我最初的想法是编写一些简单的编码器，以利用大写和小写字母和数字来缩短此字符串，使其看起来更像这样：

My initial thought was to write some simple encoder to utilize upper and lower case letters and numbers to shorten this string into something that looks more like this:

a26Dkd38JK

那是完全任意的，只是试图尽可能地清楚。
我敢肯定有一种很巧妙的方法可以做到这一点，可能已经内置了。也许这甚至是一个令人尴尬的问题。

That was completely arbitrary, just trying to be as clear as possible. I'm certain that there is a really slick way to do this, probably already built in. Maybe this is an embarrassing question to even be asking.

另外，我需要能够将缩短的字符串转换为更长的数值。
我应该编写一些东西并发布代码，还是我应该已经知道的Python函数的内置函数？

Also, I need to be able to take the shortened string and convert it back to the longer numeric value. Should I write something and post the code, or is this a one line built in function of Python that I should already know about?

谢谢！

推荐答案

这是一个很好的压缩方法：

This is a pretty good compression:

import base64

def num_to_alpha(num):
    num = hex(num)[2:].rstrip("L")

    if len(num) % 2:
        num = "0" + num

    return base64.b64encode(num.decode('hex'))

首先将整数转换为字节串，然后进行base64编码它。这是解码器：

It first turns the integer into a bytestring and then base64 encodes it. Here's the decoder:

def alpha_to_num(alpha):
    num_bytes = base64.b64decode(alpha)
    return int(num_bytes.encode('hex'), 16)

示例：

>>> num_to_alpha(20120425161608678259146181504021022591461815040210220120425161608667)
'vw4LUVm4Ea3fMnoTkHzNOlP6Z7eUAkHNdZjN2w=='
>>> alpha_to_num('vw4LUVm4Ea3fMnoTkHzNOlP6Z7eUAkHNdZjN2w==')
20120425161608678259146181504021022591461815040210220120425161608667

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