from builtins import open as _orig_open class _BkFile: def __init__(self, file, mode, bufsize): import os self.__filename = file self.__backup = file + '~' try: os.unlink(self.__backup) except OSError: pass try: os.rename(file, self.__backup) except OSError: self.__backup = None self.__file = _orig_open(file, mode, bufsize) self.closed = self.__file.closed self.fileno = self.__file.fileno self.flush = self.__file.flush self.isatty = self.__file.isatty self.mode = self.__file.mode self.name = self.__file.name self.read = self.__file.read try: self.readinto = self.__file.readinto except AttributeError: pass self.readline = self.__file.readline self.readlines = self.__file.readlines self.seek = self.__file.seek self.tell = self.__file.tell self.truncate = self.__file.truncate self.write = self.__file.write self.writelines = self.__file.writelines def close(self): self.__file.close() if self.__backup is None: return import filecmp if filecmp.cmp(self.__backup, self.__filename, shallow = 0): import os os.unlink(self.__filename) os.rename(self.__backup, self.__filename) def open(file, mode = 'r', bufsize = -1): if 'w' not in mode: return _orig_open(file, mode, bufsize) return _BkFile(file, mode, bufsize)