将具有不同长度的列表作为新列添加到数据框 [英] Adding list with different length as a new column to a dataframe
问题描述
我愿意在数据框中添加或插入列表值.数据帧len为49
,而列表ID为47
的长度.实施代码时出现以下错误.
I am willing to add or insert the list values in the dataframe. The dataframe len is 49
, whereas the length of list id 47
. I am getting the following error while implementing the code.
print("Lenght of dataframe: ",datasetTest.open.count())
print("Lenght of array: ",len(test_pred_list))
datasetTest['predict_close'] = test_pred_list
错误是:
---------------------------------------------------------------------------
ValueError Traceback (most recent call last)
<ipython-input-105-68114a4e9a82> in <module>()
5 # datasetTest = datasetTest.dropna()
6 # print(datasetTest.count())
----> 7 datasetTest['predict_close'] = test_pred_list
8 # test_shifted['color_predicted'] = test_shifted.apply(determinePredictedcolor, axis=1)
9 # test_shifted['color_original'] =
c:\python35\lib\site-packages\pandas\core\frame.py in __setitem__(self, key, value)
2517 else:
2518 # set column
-> 2519 self._set_item(key, value)
2520
2521 def _setitem_slice(self, key, value):
c:\python35\lib\site-packages\pandas\core\frame.py in _set_item(self, key, value)
2583
2584 self._ensure_valid_index(value)
-> 2585 value = self._sanitize_column(key, value)
2586 NDFrame._set_item(self, key, value)
2587
c:\python35\lib\site-packages\pandas\core\frame.py in _sanitize_column(self, key, value, broadcast)
2758
2759 # turn me into an ndarray
-> 2760 value = _sanitize_index(value, self.index, copy=False)
2761 if not isinstance(value, (np.ndarray, Index)):
2762 if isinstance(value, list) and len(value) > 0:
c:\python35\lib\site-packages\pandas\core\series.py in _sanitize_index(data, index, copy)
3119
3120 if len(data) != len(index):
-> 3121 raise ValueError('Length of values does not match length of ' 'index')
3122
3123 if isinstance(data, PeriodIndex):
ValueError: Length of values does not match length of index
如何摆脱这个错误.请帮助我.
How I can get rid of this error. Please help me.
推荐答案
如果将列表转换为Series,那么它将正常工作:
If you convert the list to a Series then it will just work:
datasetTest.loc[:,'predict_close'] = pd.Series(test_pred_list)
示例:
In[121]:
df = pd.DataFrame({'a':np.arange(3)})
df
Out[121]:
a
0 0
1 1
2 2
In[122]:
df.loc[:,'b'] = pd.Series(['a','b'])
df
Out[122]:
a b
0 0 a
1 1 b
2 2 NaN
文档将其称为通过放大设置讨论添加或扩展,但也可以在长度小于预先存在的索引的情况下使用.
The docs refer to this as setting with enlargement which talks about adding or expanding but it also works where the length is less than the pre-existing index.
要处理索引不是从0
开始还是实际上不是int的地方:
To handle where the index doesn't start at 0
or in fact is not an int:
In[126]:
df = pd.DataFrame({'a':np.arange(3)}, index=np.arange(3,6))
df
Out[126]:
a
3 0
4 1
5 2
In[127]:
s = pd.Series(['a','b'])
s.index = df.index[:len(s)]
s
Out[127]:
3 a
4 b
dtype: object
In[128]:
df.loc[:,'b'] = s
df
Out[128]:
a b
3 0 a
4 1 b
5 2 NaN
如果希望致电fillna
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