Question

我想通过遍历熊猫的每一行来添加带有列表的新列

我尝试使用df.at，但它给了我一个值错误



    import pandas as pd
    df = pd.DataFrame({'A': [1, 2, 3], 'B': ['x', 'y', 'z']})
    for index, row in df.iterrows():
        df.at[index,'new_col'] = ['m','n']

实际结果：



    Traceback (most recent call last):
      File "D:/Projects/fasttextproj/test.py", line 10, in 
        df.at[index,'new_col'] = ['m','n']
      File "D:\Projects\fasttext\lib\site-packages\pandas\core\indexing.py", line 2287, in __setitem__
        self.obj._set_value(*key, takeable=self._takeable)
      File "D:\Projects\fasttext\lib\site-packages\pandas\core\frame.py", line 2823, in _set_value
        self.loc[index, col] = value
      File "D:\Projects\fasttext\lib\site-packages\pandas\core\indexing.py", line 190, in __setitem__
        self._setitem_with_indexer(indexer, value)
      File "D:\Projects\fasttext\lib\site-packages\pandas\core\indexing.py", line 366, in _setitem_with_indexer
        self._setitem_with_indexer(new_indexer, value)
      File "D:\Projects\fasttext\lib\site-packages\pandas\core\indexing.py", line 611, in _setitem_with_indexer
        raise ValueError('Must have equal len keys and value '
    ValueError: Must have equal len keys and value when setting with an iterable

Answer 1

尝试：

df['new_col'] = [['m', 'n']] * df.shape[0]

Answer 2

您还可以使用：

df['new_col'] = [['m', 'n'] for i in df.index]

或者

df =df.assign(new_col = [['m', 'n'] for i in df.index])

如何在熊猫的新列中添加列表？

2 个答案: