在idles上输入：
>import statsmodels
>
没有出现错误 ；
但是输入：
>import statsmodels.api  as sm
Traceback (most recent call last):
  File "<pyshell#23>", line 1, in <module>
    import statsmodels.api  as sm
  File "D:\Python27\lib\site-packages\statsmodels\api.py", line 5, in <module>
    from . import regression
  File "D:\Python27\lib\site-packages\statsmodels\regression\__init__.py", line 1, in <module>
    from .linear_model import yule_walker
  File "D:\Python27\lib\site-packages\statsmodels\regression\linear_model.py", line 53, in <module>
    import statsmodels.base.model as base
  File "D:\Python27\lib\site-packages\statsmodels\base\model.py", line 14, in <module>
    from statsmodels.formula import handle_formula_data
  File "D:\Python27\lib\site-packages\statsmodels\formula\__init__.py", line 4, in <module>
    from .formulatools import handle_formula_data
  File "D:\Python27\lib\site-packages\statsmodels\formula\formulatools.py", line 3, in <module>
    from patsy import dmatrices, NAAction
ImportError: No module named patsy

出现错误；
什么原因啊？
求各路大神给予意见解决~~~~
万分感谢！！！！！！！！！！！！！