Python3 交互模式 next(文件) 之后 文件.tell() OSError 恢复的问题？

Question

交互模式输入：

f = open( "Config.h", "r+", encoding="UTF-8" )
next(f)
f.tell()

这样会报错：

OSError: telling position disabled by next() call

原因可以理解
但是之后再在交互模式里输入 f.tell() 会报一样的错误
想来是 disabled by next() 还没被恢复
但是 f.seek 重设置一下之后 f.tell 就不会报错了
想问下具体细节是怎样的？
disabled by next() 如何被恢复的？
PS：呃，忘了说，是 Python3……
PS：我知道这是异常……

Answer 1

SAD, I finally solved it myself...
The next source code of the file io set the flag bit

def __next__(self):
    self._telling = False
    line = self.readline()
    if not line:
        self._snapshot = None
        self._telling = self._seekable
        raise StopIteration
    return line

tell will detect the flag

if not self._telling:
    raise OSError("telling position disabled by next() call")

seek will clear the flag (there are too many code distributions so I won’t post it)
Look for the source code yourself for details...