Python ValueError：无法设置没有定义索引的框架和无法转换为系列的值
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ValueError: Cannot set a frame with no defined index and a value that cannot be converted to a Series
提问by Tanvi Mirza
I'm using Pandas 0.20.3 in my python 3.X. I want to add one column in a pandas data frame from another pandas data frame. Both the data frame contains 51 rows. So I used following code:
我在 python 3.X 中使用 Pandas 0.20.3。我想在另一个熊猫数据框中的熊猫数据框中添加一列。两个数据框都包含 51 行。所以我使用了以下代码：
class_df['phone']=group['phone'].values
I got following error message:
我收到以下错误消息：
ValueError: Cannot set a frame with no defined index and a value that cannot be converted to a Series
class_df.dtypes gives me:
class_df.dtypes 给了我：
Group_ID object
YEAR object
Terget object
phone object
age object
and type(group['phone'])returns pandas.core.series.Series
并type(group['phone'])返回pandas.core.series.Series
Can you suggest me what changes I need to do to remove this error?
您能否建议我需要做哪些更改才能消除此错误？
The first 5 rows of group['phone'] are given below:
group['phone'] 的前 5 行如下所示：
0 [735015372, 72151508105, 7217511580, 721150431...
1 []
2 [735152771, 7351515043, 7115380870, 7115427...
3 [7111332015, 73140214, 737443075, 7110815115...
4 [718218718, 718221342, 73551401, 71811507...
Name: phoen, dtype: object
采纳答案by cs95
You have a column of ragged lists. Your only option is to assign a list of lists, and not an arrayof lists (which is what .valuegives).
您有一列参差不齐的列表。您唯一的选择是分配一个列表列表，而不是一个列表数组（这是.value给出的）。
class_df['phone'] = group['phone'].tolist()
回答by Jefferson Sankara
In most cases, this error comes when you return an empty dataframe. The best approach that worked for me was to check if the dataframe is empty first before using apply()
在大多数情况下，当您返回空数据帧时会出现此错误。对我有用的最佳方法是在使用 apply() 之前先检查数据框是否为空
if len(df) != 0:
df['indicator'] = df.apply(assign_indicator, axis=1)
回答by Essi A.
Instead of using an if-statement, you can use set result_typeargument of apply()function to "reduce".
您可以使用apply()函数的setresult_type参数来“减少” ，而不是使用 if 语句。
df['new_column'] = df.apply(func, axis=1, result_type='reduce')
回答by Thomas R
The error of the Question-Headline
问题标题的错误
"ValueError: Cannot set a frame with no defined index and a value that cannot be converted to a Series"
“ValueError：无法设置没有定义索引的框架和无法转换为系列的值”
might as well occur if for what ever reason the table does not have any rows.
如果由于某种原因表没有任何行，也可能发生。
