>>> print('rate is %')

rate is %

>>> print('rate is %d%')

rate is %d%

>>> print('rate is %d%'%9)

Traceback (most recent call last):

  File "<stdin>", line 1, in <module>

ValueError: incomplete format

我发现最后这个，是因为有了%9，前面的才会被识别成 占位符？所以报错？