ValueError:设置具有序列的数组元素. pandas [英] ValueError: setting an array element with a sequence. for Pandas

问题描述

我有一个Pandas dataframe，称为output.基本问题是我想使用ix函数将dataframe中的某一行，列设置为列表，并得到ValueError: setting an array element with a sequence.我的理解是dataframe元素就像一个list元素，它可以容纳任何内容(字符串，列表，元组等).我不正确吗?

I have a Pandas dataframe, called output. The basic issue is that I would like to set a certain row, column in the dataframe to a list using the ix function and am getting ValueError: setting an array element with a sequence. My understanding is that a dataframe element was like a list element, it could hold anything (string, list, tuple, etc). Am I not correct?

基本设置:

import pandas as pd
output = pd.DataFrame(data = [[800.0]], columns=['Sold Count'], index=['Project1'])
print output.ix['Project1', 'Sold Count']
>>>800

工作正常

output.ix['Project1', 'Sold Count'] = 400.0
print output.ix['Project1', 'Sold Count']
>>>400.0    

不起作用

output.ix['Project1', 'Sold Count'] = [400.0]
print output.ix['Project1', 'Sold Count']
>>>ValueError: setting an array element with a sequence.

推荐答案

如果您确实想将列表设置为元素的值，则问题在于创建DataFrame时列的dtype， dtype被推断为float64，因为它仅包含数字值.

If you really want to set a list as the value for the element, the issue is with the dtype of the column, when you create the DataFrame, the dtype gets inferred as float64 , since it only contains numeric values.

然后，当您尝试将列表设置为值时，由于dtype，它会出错.解决此问题的一种方法是使用非数字dtype(例如object).示例-

Then when you try to set a list as the value, it errors out, due to the dtype . A way to fix this would be to use a non-numeric dtype (like object) or so. Example -

output['Sold Count'] = output['Sold Count'].astype(object)
output.loc['Project1','Sold Count'] = [1000.0,800.0] #Your list

演示-

In [91]: output = pd.DataFrame(data = [[800.0]], columns=['Sold Count'], index=['Project1'])

In [92]: output
Out[92]:
          Sold Count
Project1         800

In [93]: output['Sold Count'] = output['Sold Count'].astype(object)

In [94]: output.loc['Project1','Sold Count'] = [1000.0,800.0]

In [95]: output
Out[95]:
               Sold Count
Project1  [1000.0, 800.0]

---

您还可以在创建DataFrame时指定dtype，示例-

---

You can also specify the dtype while creating the DataFrame, Example -

output = pd.DataFrame(data = [[800.0]], columns=['Sold Count'], index=['Project1'],dtype=object)
output.loc['Project1','Sold Count'] = [1000.0,800.0]

演示-

In [96]: output = pd.DataFrame(data = [[800.0]], columns=['Sold Count'], index=['Project1'],dtype=object)

In [97]: output.loc['Project1','Sold Count'] = [1000.0,800.0]

In [98]: output
Out[98]:
               Sold Count
Project1  [1000.0, 800.0]

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