Question

我在教自己如何使用Python3。我想训练我获得的技能并编写命令行备份程序。我正在尝试使用Shelve模块保存默认备份并保存位置，但似乎它会在我关闭或重新启动程序时忘记我保存的变量。

这是与货架配合使用的主要功能：

def WorkShelf(key, mode='get', variable=None):
    """Either stores a variable to the shelf or gets one from it.
    Possible modes are 'store' and 'get'"""
    config = shelve.open('Config')

    if mode.strip() == 'get':
        print(config[key])
        return config[key]

    elif mode.strip() == 'store':
        config[key] = variable
        print(key,'holds',variable)

    else:
        print("mode has not been reconginzed. Possible modes:\n\t- 'get'\n\t-'store'")

    config.close()

因此，每当我调用此函数来存储变量并在此之后调用函数时，它就能完美地运行。我试图手动访问货架，一切都在那里。这是用于存储变量的代码：

WorkShelf('BackUpPath','store', bupath)
WorkShelf('Path2BU', 'store', path)

当我在重新启动脚本后尝试从架子上获取变量时出现问题。这段代码：

config = shelve.open('Config')
path = config['Path2BU']
bupath = config['BackUpPath']

给我这个错误：

Traceback (most recent call last):
  File "C:\Python35-32\lib\shelve.py", line 111, in __getitem__
    value = self.cache[key]
KeyError: 'Path2BU'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "<pyshell#2>", line 1, in <module>
    config['Path2BU']
  File "C:\Python35-32\lib\shelve.py", line 113, in __getitem__
    f = BytesIO(self.dict[key.encode(self.keyencoding)])
  File "C:\Python35-32\lib\dbm\dumb.py", line 141, in __getitem__
    pos, siz = self._index[key]     # may raise KeyError
KeyError: b'Path2BU

基本上，这是我可以通过调用ShelveObject ['ThisKeyDoesNotExist']重现的错误。

我现在真的迷失了。当我尝试手动创建一个架子，关闭它并再次访问它似乎工作（即使我之前有错误）现在。我已经阅读了关于这个的每一篇文章，我想到了书架腐败（但它不太可能每次都发生），而且我现在已经读过我的剧本A到Z大约20次了。

感谢您的帮助（我希望这次能以正确的方式提出我的问题）！

修改

好的，这让我发疯了。隔离WorkShelf（）确实可以正常工作，如下所示：

import shelve

    def WorkShelf(key, mode='get', variable=None):
        """Either stores a variable to the shelf or gets one from it.
        Possible modes are 'store' and 'get'"""
        config = shelve.open('Config')

        if mode.strip() == 'get':
            print(config[key])
            return config[key]

        elif mode.strip() == 'store':
            config[key] = variable
            print(key,'holds',variable)

        else:
            print("mode has not been reconginzed. Possible modes:\n\t- 'get'\n\t-'store'")

        config.close()

    if False:
        print('Enter path  n1: ')
        path1 = input("> ")
        WorkShelf('Path1', 'store', path1)

        print ('Enter path n2: ')
        path2 = input("> ")
        WorkShelf('Path2', 'store', path2)

    else:
        path1, path2 = WorkShelf('Path1'), WorkShelf('Path2')
        print (path1, path2)

没问题，完美。

但是当我在我的脚本中使用相同的函数时，我得到了这个输出。它基本上告诉我确实将变量写入搁置文件（'此键保存此变量'消息）。我甚至可以使用重启时使用的相同代码来调用它们。但是在程序重置后调用它们时，就像'你在说什么？我从来没有救过这些'。

Welcome to this backup manager.
We will walk you around creating your backup and backup preferences

What directory would you like to backup?
Enter path here: W:\Users\Damien\Documents\Code\Code Pyth
Would you like to se all folders and files at that path? (enter YES|NO)
> n


Okay, let's proceed.
Where would you like to create your backup?
Enter path here: N:\

Something already exists there: 
19 folders and 254 documents

Would you like to change your location?
> n
Would you like to save this destination (N:\) as your default backup location ?    That way you don't have to type it again.
> y
BackUpPath holds N:\

If you're going to be backing the same data up we can save the files location W:\Users\Damien\Documents\Code\Code Pyth    so you don't have to type all the paths again.
Would you like me to remember the backup file's location?
> y
Path2BU holds W:\Users\Damien\Documents\Code\Code Pyth
>>> 
======== RESTART: W:\Users\Damien\Documents\Code\Code Pyth\Backup.py ========
Welcome to this backup manager.
Traceback (most recent call last):
  File "C:\Python35-32\lib\shelve.py", line 111, in __getitem__
    value = self.cache[key]
KeyError: 'Path2BU'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "W:\Users\Damien\Documents\Code\Code Pyth\Backup.py", line 198, in <module>
    path, bupath = WorkShelf('Path2BU'), WorkShelf('BackUpPath')
  File "W:\Users\Damien\Documents\Code\Code Pyth\Backup.py", line 165, in WorkShelf
    print(config[key])
  File "C:\Python35-32\lib\shelve.py", line 113, in __getitem__
    f = BytesIO(self.dict[key.encode(self.keyencoding)])
  File "C:\Python35-32\lib\dbm\dumb.py", line 141, in __getitem__
    pos, siz = self._index[key]     # may raise KeyError
KeyError: b'Path2BU'

请帮助，我疯了，可能会开发一个类来存储和从文本文件中获取变量。

Answer 1

好的，我刚刚发现了什么问题。

我的设置代码中有一个os.chdir（）。每当安装完成并且我想打开我的配置文件时，它会查看当前目录，但是货架位于设置中指向的目录os.chdir（）中。

由于某种原因，我最终在目录中的空架子上实际应该是。这花了我一天的调试。

这对今天的人来说都是如此！

Shelve一直忘记它所拥有的变量

1 个答案: