Python '<'；在'；str'；和'；int'；，但是在数据中找不到字符串

我发现了这个错误

“你能举一个数据帧的小例子吗？总是把完整的错误信息（从单词“Traceback”开始）作为文本（不是截图）放在问题中（不是评论）。还有其他有用的信息。很抱歉最后的答案。我包括了完整的错误和部分数据帧。你能举一个数据帧的小例子吗？总是把完整的错误消息（从单词“Traceback”开始）作为文本（不是截图）放在问题中（不是评论）。还有其他有用的信息。很抱歉最后的答案。我包括了全部错误和部分数据帧。
zi_diff_2017 = data_red_tot.iloc[:,2:6][(data_red_tot["year"] == 2017)].subtract(data_red_tot.iloc[:,2:6][(data_red_tot["year"] == 2016)])

zi_diff_2018 = data_red_tot.iloc[:,2:6][(data_red_tot["year"] == 2018)].subtract(data_red_tot.iloc[:,2:6][(data_red_tot["year"] == 2017)])

zi_diff_2016 = data_red_tot.iloc[:,2:6][(data_red_tot["year"] == 2016)].subtract(data_red_tot.iloc[:,2:6][(data_red_tot["year"] == 2015)])

data_red_tot.iloc[:,2:6][(data_red_tot["year"] == 2016)].info()
<class 'pandas.core.frame.DataFrame'>
Index: 431 entries, 1 to 9866
Data columns (total 4 columns):
b    431 non-null float64
s    431 non-null float64
si    431 non-null float64
i    431 non-null float64
dtypes: float64(4)
memory usage: 16.8+ KB

data_red_tot.iloc[:,2:6][(data_red_tot["year"] == 2017)].info()
<class 'pandas.core.frame.DataFrame'>
Index: 431 entries, 1 to 9866
Data columns (total 4 columns):
b    431 non-null float64
s    431 non-null float64
si    431 non-null float64
i     431 non-null float64
dtypes: float64(4)
memory usage: 16.8+ KB

Traceback (most recent call last):

  File "<ipython-input-219-66f6f768e275>", line 1, in <module>
    zi_diff_2017 = data_red_tot.iloc[:,2:6][(data_red_tot["jahr"] == 2017)].subtract(data_red_tot.iloc[:,2:6][(data_red_tot["jahr"] == 2016)])

  File "C:\Users\BaranCalisci\AppData\Local\Continuum\anaconda3\lib\site-packages\pandas\core\ops\__init__.py", line 1493, in f
    return self._combine_frame(other, pass_op, fill_value, level)

  File "C:\Users\BaranCalisci\AppData\Local\Continuum\anaconda3\lib\site-packages\pandas\core\frame.py", line 5359, in _combine_frame
    this, other = self.align(other, join="outer", level=level, copy=False)

  File "C:\Users\BaranCalisci\AppData\Local\Continuum\anaconda3\lib\site-packages\pandas\core\frame.py", line 3939, in align
    broadcast_axis=broadcast_axis,

  File "C:\Users\BaranCalisci\AppData\Local\Continuum\anaconda3\lib\site-packages\pandas\core\generic.py", line 8811, in align
    fill_axis=fill_axis,

  File "C:\Users\BaranCalisci\AppData\Local\Continuum\anaconda3\lib\site-packages\pandas\core\generic.py", line 8850, in _align_frame
    other.index, how=join, level=level, return_indexers=True

  File "C:\Users\BaranCalisci\AppData\Local\Continuum\anaconda3\lib\site-packages\pandas\core\indexes\base.py", line 3572, in join
    other, how=how, return_indexers=return_indexers

  File "C:\Users\BaranCalisci\AppData\Local\Continuum\anaconda3\lib\site-packages\pandas\core\indexes\base.py", line 3884, in _join_monotonic
    join_index, lidx, ridx = self._outer_indexer(sv, ov)

  File "C:\Users\BaranCalisci\AppData\Local\Continuum\anaconda3\lib\site-packages\pandas\core\indexes\base.py", line 247, in _outer_indexer
    return libjoin.outer_join_indexer(left, right)

  File "pandas\_libs\join.pyx", line 563, in pandas._libs.join.outer_join_indexer

TypeError: '<' not supported between instances of 'str' and 'int'

 data_red_tot.iloc[:,2:6][(data_red_tot["year"] == 2017)]
Out[222]: 
      b            s           si         i
mnr                                                
1      76.420562   75.925346   80.022474  78.318538
1014   59.594468   72.901359   72.282378  60.533343
1036   61.411302   61.989852   72.520348  65.580230
1040   67.211456   70.899914   79.363689  75.096387
1061   50.524718   49.964110   73.015946  59.057265
         ...         ...         ...        ...
9517   72.322934   68.839042   76.055376  74.890859
9519   58.167611   57.518538   65.719448  65.140976
964    72.290164   73.651271   74.162528  70.824842
968    51.930839   56.682868   63.408826  59.901983
9866   65.514969   59.013144   67.161826  69.747105

[431 rows x 4 columns]

data_red_tot.iloc[:,2:6][(data_red_tot["year"] == 2016)]
Out[223]: 
      b            s           si         i
mnr                                                
1      76.854202   74.451864   79.998974  78.063673
4      58.976897   67.254973   71.951488  71.543260
27     71.128836   64.647496   72.204597  71.105160
28     52.317802   66.144949   64.518158  63.351971
53     65.253281   55.666438   69.048888  68.434020
         ...         ...         ...        ...
9517   53.312900   55.207277   67.526596  62.432935
9519   59.509448   61.668949   77.609081  66.764866
9519   59.509448   61.668949   77.609081  66.764866
9866   65.513959   61.555514   67.611603  71.011886
9866   65.513959   61.555514   67.611603  71.011886

[431 rows x 4 columns]