在 Pandas 的整数数据框中使用 DataFrame.at

Question

我有以下DataFrame由整数值组成的内容：

df = pd.DataFrame(data=1, columns=['a','b'], index=[1,2,3])

   a  b

1  1  1

2  1  1

3  1  1

我想在单个单元格上设置缺失值，当我尝试时：

df.at[1,'a'] = np.nan

然后我得到这个异常：

Traceback (most recent call last):

  File "<input>", line 1, in <module>

  File "pandas/core/indexing.py", line 2159, in __setitem__

    self.obj._set_value(*key, takeable=self._takeable)

  File "pandas/core/frame.py", line 2582, in _set_value

    engine.set_value(series._values, index, value)

  File "pandas/_libs/index.pyx", line 124, in pandas._libs.index.IndexEngine.set_value

  File "pandas/_libs/index.pyx", line 133, in pandas._libs.index.IndexEngine.set_value

  File "pandas/_libs/index.pyx", line 570, in pandas._libs.index.convert_scalar

ValueError: Cannot assign nan to integer series