Question

我正在尝试自定义用于url = 'https://bing.com' + url和python 2.7（至少python 3.x）的库中文件句柄的行为。

我正在实现的自定义行为要求在调用>=3.6方法时必须执行某些操作，无论是直接（close）还是fh.close()方法的结果。

我也在尝试添加其他方法-叫它__exit__()。

我的理想世界是为用户提供一个可以正常使用的文件句柄（读/读线/写/ ...），但在幕后还要有一些特殊的逻辑。

这是我目前正在使用的东西...

custom_copy()

以上代码在from os import fsync def custom_open(filepath, mode='rt', *args **kwargs): # Open the file normally using open_args orig_file_handle = open(filepath, mode, *args, **kwargs) # pylint: disable=star-args # Preserve original close function original_close_fn = orig_file_handle.close # Create a custom close function def custom_close_fn(*args, **kwargs): original_close_fn(*args, **kwargs) print("Do Something Custom") orig_file_handle.close = custom_close_fn # Add custom_copy function def custom_copy_fn(*args, **kwargs): if orig_file_handle.closed: raise ValueError("I/O operation on closed file") # Ensure buffer has been flushed before rsync orig_file_handle.flush() fsync() return _my_custom_copy(filepath, *args, **kwargs) orig_file_handle.custom_copy = custom_copy_fn return orig_file_handle中有效，但是在python3.7.0中却失败了

python2.7.8

我还尝试了另一种涉及子类化> orig_file_handle.close = custom_close_fn E AttributeError: 'file' object attribute 'close' is read-only的方法，但是还有其他一些问题...

type(orig_file_handle)

在def custom_open(filepath, mode='rt', open_args=None): open_args = open_args or {} open_args['mode'] = mode # Open the file normally using open_args orig_file_handle = open(filepath, **open_args) # pylint: disable=star-args class CustomFile(type(orig_file_handle)): def __init__(self, file_handle): # pylint: disable=super-init-not-called self.__dict__ = file_handle.__dict__.copy() def close(self, *args, **kwargs): # Execute normal file handle close super(CustomFile, self).close(*args, **kwargs) print("Do Something Custom") def custom_copy(self, *args, **kwargs): if self.closed: # pylint: disable=no-member raise ValueError("I/O operation on closed file") self.flush() # pylint: disable=no-member fsync() return _my_custom_copy(filepath, *args, **kwargs) return CustomFile(orig_file_handle)中，此失败并显示

python2.7.8

在> self.__dict__ = file_handle.__dict__.copy() E AttributeError: 'file' object has no attribute '__dict__'中，它失败并

python3.7.0

有什么想法可以解决此问题，或者我应该遵循其他模式才能获得想要的结果吗？

一吨！

Answer 1

请勿继承，修饰：

class CustomFile:                                  
        def __init__(self, file_handle):                                       
            # pylint: disable=super-init-not-called                            
            self._f = file_handle                       

        def close(self, *args, **kwargs):                                      
            self._f.close(*args,**kwargs)   
            print("Do Something Custom")
            self.closed = True

编辑

This recipe关于代理对象也很好

从python的'File'类继承并定义自定义行为-python2和3

1 个答案: