在解析pdf檔的內文時，使用了tabula + pandas模組的concat
但在解析concat出來的值時出現KeyError

#pdf 轉文字

try:
        df=tabula.read_pdf(input_path=pdffile, output_format='dataframe', lattice=True, multiple_tables=True, pages="all", guess=False,
                                   encoding='utf-8')
        df = pd.concat(df)
    except Exception as e:
        print(e)
    df.to_csv("outing.csv", index = None, header=True)
    get_sh_content(df)

#讀取

def get_sh_content(df):
        ans = []
        print(len(df.index))
        df.fillna(0)
        print(df[df.columns[0]][len(df.index)])

會出現error：

File "test.py", line 44, in get_sh_content
    print(df[df.columns[0]][len(df.index)])
  File "C:\Users\user\Anaconda3\lib\site-packages\pandas\core\series.py", line 1068, in __getitem__
    result = self.index.get_value(self, key)
  File "C:\Users\user\Anaconda3\lib\site-packages\pandas\core\indexes\base.py", line 4730, in get_value
    return self._engine.get_value(s, k, tz=getattr(series.dtype, "tz", None))
  File "pandas\_libs\index.pyx", line 80, in pandas._libs.index.IndexEngine.get_value
  File "pandas\_libs\index.pyx", line 88, in pandas._libs.index.IndexEngine.get_value
  File "pandas\_libs\index.pyx", line 126, in pandas._libs.index.IndexEngine.get_loc
  File "pandas\_libs\index.pyx", line 152, in pandas._libs.index.IndexEngine._get_loc_duplicates
  File "pandas\_libs\index_class_helper.pxi", line 122, in pandas._libs.index.Int64Engine._maybe_get_bool_indexer
KeyError: 5237

請問是因為當中有NA值還是其他問題會造成呢？
嘗試將資料輸出成csv檔查看，發現空值很多，試過用fillna替換，也沒辦法解決。
懇求會的大大提點！