将一个元组添加到大 pandas 数据帧的特定单元格中

问题描述

只是当我以为我正在摆脱Python和熊猫时，另一个看似简单的问题就出现了。我想添加元组到大熊猫数据帧的特定单元格。这些元组需要根据数据帧中其他单元格的内容即时计算 - 换句话说，我不能提前计算所有元组，并将它们作为单个数组添加。

作为一个例子，我用一些数据定义了一个数据框，并添加了几个空列：

  import pandas as pd 
 import bumpy as np 
 tempDF = pd.DataFrame（{'miscdata'：[1.2,3.2,4.1,2.3,3.3,2.5,4.3,2.5,2.2,4.2] }）
 tempDF ['newValue'] = np.nan 
 tempDF ['newTuple'] = np.nan 
  

我可以滚动newValue列的每个单元格，并添加一个整数值，没有问题：

  anyOldValue = 3.5 
 for i in range（10）：
 tempDF.ix [（i，'newValue'）] = anyOldValue 
 
 print tempDF 
  

但是，如果我尝试添加一个元组，我会收到一条错误消息：

  anyOldTuple =（2.3,4.5）
 for i in range（10）：
 temp DF.ix [（i，'newTuple'）] = anyOldTuple 
 
打印tempDF 
  

我收到了几个错误信息，包括：

  ValueError：设置ndarray时必须具有相同的len键和值
  

...和...

  ValueError：设置一个有序列的数组元素。 
  

我确定我已经看到了单元格中的元组（或列表）的数据框 - 避风港我不是吗任何建议，如何使这个代码工作将非常感谢。

解决方案

您可以使用 set_value ：

  tempDF.set_value（i，'newTuple'，anyOldTuple）
  

还要确保列不是浮动列，例如：

  tempDF ['newTuple'] ='s'或设置dtype 
  

否则您将收到错误。

Just when I thought I was getting the hang of Python and Pandas, another seemingly simple issue crops up. I want to add tuples to specific cells of a pandas dataframe. These tuples need to be calculated on-the-fly based on the contents of other cells in the dataframe - in other words, I can't easily calculate all tuples in advance and add them as a single array.

As an example, I define a dataframe with some data and add a couple of empty columns:

import pandas as pd
import bumpy as np
tempDF = pd.DataFrame({'miscdata': [1.2,3.2,4.1,2.3,3.3,2.5,4.3,2.5,2.2,4.2]})
tempDF['newValue'] = np.nan
tempDF['newTuple'] = np.nan

I can scroll through each cell of the 'newValue' column and add an integer value without problems:

anyOldValue = 3.5
for i in range(10):
    tempDF.ix[(i,'newValue')] = anyOldValue

print tempDF

However, if I try to add a tuple I get an error message:

anyOldTuple = (2.3,4.5)
for i in range(10):
    tempDF.ix[(i,'newTuple')] = anyOldTuple

print tempDF

I've received several error messages including:

ValueError: Must have equal len keys and value when setting with an ndarray

…and…

ValueError: setting an array element with a sequence.

I'm sure I've seen data frames with tuples (or lists) in the cells - haven't I? Any suggestions how to get this code working would be much appreciated.

解决方案

You can use set_value:

tempDF.set_value(i,'newTuple', anyOldTuple)

Also make sure that the column is not a float column, for example:

tempDF['newTuple'] = 's' # or set the dtype

otherwise you will get an error.

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