tempfile.py 文件源码

def rollover(self):
        if self._rolled: return
        file = self._file
        newfile = self._file = TemporaryFile(**self._TemporaryFileArgs)
        del self._TemporaryFileArgs

        newfile.write(file.getvalue())
        newfile.seek(file.tell(), 0)

        self._rolled = True

    # The method caching trick from NamedTemporaryFile
    # won't work here, because _file may change from a
    # BytesIO/StringIO instance to a real file. So we list
    # all the methods directly.

    # Context management protocol