code: def write_file(self, new_text, filename, old_text, encoding=None):
          
          try:
              f = _open_with_encoding(filename, "w", encoding=encoding)
          except os.error as err:
              self.log_error("Can't create %s: %s", filename, err)
              return
          try:
              f.write(_to_system_newlines(new_text))
          except os.error as err:
              self.log_error("Can't write %s: %s", filename, err)
          finally:
              f.close()
          self.log_debug("Wrote changes to %s", filename)
          self.wrote = True
docs: Writes a string to a file.
  
          It first shows a unified diff between the old text and the new text, and
          then rewrites the file; the latter is only done if the write option is
          set.