ImportError：无法导入名称＆＃39; PyvtTbl＆＃39;

Question

当我尝试导入PyvtTbl和DataFrame时，会出现此错误。

    ImportError                               Traceback (most recent call last)
<ipython-input-35-452740a411c0> in <module>()
----> 1 from pyvttbl import DataFrame
      2 from base import PyvtTbl, DataFrame

~\AppData\Local\Continuum\lib\site-packages\pyvttbl\__init__.py in <module>()
      8 # This software is funded in part by NIH Grant P20 RR016454.
      9 
---> 10 from base import PyvtTbl, DataFrame
     11 
     12 from misc import *

ImportError: cannot import name 'PyvtTbl'

我已经使用pip install安装了这些软件包。