奇怪的键错误 || Python3.6.1

Question

我正在尝试在 python 中制作类似 FileSystem 的东西。我的目标是制作可以包含一些数据的文件和可以包含一些文件的目录。然后我有一些简单的命令

cd
ls
mk_dir
mk_file

所以，现在我遇到了一个问题： DirectoryBase class 与Directory 不同，因为它没有ParentDir（其中的Directory File/Directory 已保存）。然后是 Directory class 扩展 DirectoryBase 并覆盖 path() 方法（方法 returning 到 file/dir 的路径）并且数据字典有另一个默认键：'..'，但是当我试图在数据字典中找到它会引发 KeyError。另一件奇怪的事情是，我正在测试 file/dir 是否存在，如果不存在，它将 return，所以我不知道这是怎么可能的，它得到了 KeyError.

这是我的代码：

class AttributeDictionary(dict):
    def __init__(self, **kwargs):
        super().__init__(**kwargs)
        self.__getattr__ = self.__getitem__
        self.__setattr__ = self.__setitem__
        self.__delattr__ = self.__delitem__


class FileManager(object):
    def __init__(self):
        self.disk_dir = DirectoryBase('__disk__')
        self.current_dir = self.disk_dir

    def _find(self, path):
        """ Gets file/dir object using path """
        _cd = self.current_dir
        for part in path:
            _cd = _cd[part]
        return _cd

    def cmd_cd(self, path):
        """ Classic unix `cd` command """
        f = self._find(path)
        if f is DirectoryBase:
            self.current_dir = f
        else:
            return FileSystemError('DirectoryNotFound')

    def cmd_ls(self):
        """ Classic unix `ls` command """
        return ConsoleOutput(''.join([f'{i}\n' for i in self.current_dir.data]))

    def cmd_mkfile(self, name):
        """ file making command """
        self.current_dir.__setitem__(name, File(name, self.current_dir))

    def cmd_mkdir(self, name):
        """ file making command """
        self.current_dir.__setitem__(name, Directory(name, self.current_dir))


class File(object):
    def __init__(self, name, pd):
        self.data = [0x00]
        self.name = name
        self.pd = pd

    def path(self):
        return [self.name] + self.pd.path()

    def __sizeof__(self):
        return len(self.data)


class DirectoryBase(AttributeDictionary):
    def __init__(self, name, **kwargs):
        super().__init__(**kwargs)
        self.name = name
        self.data = {'.': self}

    def path(self):
        return self.name

    def __getitem__(self, item):
        if item in self.data.keys():
            return FileSystemError('FileNotFound')
        return self.data[item] # KeyError: '..' found here

    def __setitem__(self, key, value):
        if key in self.data.keys():
            return FileSystemError('FileAlreadyExists')
        self.data[key] = value

    def __delitem__(self, key):
        if key in self.data.keys():
            return FileSystemError('FileNotFound')
        self.data.__delitem__(key)


class Directory(DirectoryBase):
    def __init__(self, name, pd, **kwargs):
        super().__init__(name, **kwargs)
        self.pd = pd
        self.data = {'.': self, '..': self.pd}

    def path(self):
        return [self.name] + self.pd.path()


if __name__ == '__main__':
    fs = FileManager()
    fs.cmd_mkdir('test')
    print(fs.cmd_ls())
    fs.cmd_cd(['test'])
    fs.cmd_mkfile('idk.txt')
    print(fs.cmd_ls())
    fs.cmd_cd(['..'])
    print(fs.cmd_ls())

错误如下所示：

.
test
Traceback (most recent call last):

.
  File "/Users/jan/PycharmProjects/Xaon/src/fs.py", line 106, in <module>
test
    fs.cmd_cd(['..'])
idk.txt

  File "/Users/jan/PycharmProjects/Xaon/src/fs.py", line 32, in cmd_cd
    f = self._find(path)
  File "/Users/jan/PycharmProjects/Xaon/src/fs.py", line 27, in _find
    _cd = _cd[part]
  File "/Users/jan/PycharmProjects/Xaon/src/fs.py", line 76, in __getitem__
    return self.data[item]
KeyError: '..'

或者当我删除照片时：

Traceback (most recent call last):
  File "/Users/jan/PycharmProjects/Xaon/src/fs.py", line 106, in <module>
    fs.cmd_cd(['..'])
  File "/Users/jan/PycharmProjects/Xaon/src/fs.py", line 32, in cmd_cd
    f = self._find(path)
  File "/Users/jan/PycharmProjects/Xaon/src/fs.py", line 27, in _find
    _cd = _cd[part]
  File "/Users/jan/PycharmProjects/Xaon/src/fs.py", line 76, in __getitem__
    return self.data[item]
KeyError: '..'

对不起，如果太混乱了，我是初学者，我的英语也不好。

Answer 1

代码逻辑有问题：

def __getitem__(self, item):
    if item in self.data.keys():
        return FileSystemError('FileNotFound')
    return self.data[item] # KeyError: '..' found here

当键存在时，您将抛出错误。只需否定条件（并在 Python 2 中删除无用且非 pythonic 甚至性能杀手的 .keys()）：

def __getitem__(self, item):
    if item not in self.data:
        return FileSystemError('FileNotFound')
    return self.data[item]

__delitem__ BTW 中也有同样的错误。

修复后（并用 str 对 unexisting/unshown 类的大部分进行了存根），我得到以下输出：

.
test

.
idk.txt
test

.
idk.txt
test

奇怪的键错误 || Python3.6.1

Weird KeyError || Python3.6.1

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