Pandas - 使用其他列值作为列名选择列 [英] Pandas - select column using other column value as column name

问题描述

我有一个包含一列的数据框，我们称之为名称".名称"具有其他列的名称.我想添加一个新列，该列将根据名称"中包含的列名称为每一行提供值.列.

示例:

输入数据框:pd.DataFrame.from_dict({"a": [1, 2, 3,4], "b": [-1,-2,-3,-4], "names":['a','b','a','b']})

<前>|乙 |姓名 |--- |--- |---- |1 |-1 |'一个' |2 |-2 |'b' |3 |-3 |'一个' |4 |-4 |'b' |

输出数据帧:pd.DataFrame.from_dict({"a": [1, 2, 3,4], "b": [-1,-2,-3,-4], "names":['a','b','a','b'], "new_col":[1,-2,3,-4]})

<前>|乙 |姓名 |new_col |--- |--- |---- |------ |1 |-1 |'一个' |1 |2 |-2 |'b' |-2 |3 |-3 |'一个' |3 |4 |-4 |'b' |-4 |

解决方案

您可以使用 查找:

df['new_col'] = df.lookup(df.index, df.names)df# a b 命名为 new_col#0 1 -1 1#1 2 -2 b -2#2 3 -3 3#3 4 -4 b -4

I have a dataframe that contains a column, let's call it "names". "names" has the name of other columns. I would like to add a new column that would have for each row the value based on the column name contained on that "names" column.

Example:

Input dataframe: pd.DataFrame.from_dict({"a": [1, 2, 3,4], "b": [-1,-2,-3,-4], "names":['a','b','a','b']})

  a  |  b  | names |
 --- | --- | ----  |
  1  |  -1 | 'a'   |
  2  |  -2 | 'b'   |
  3  |  -3 | 'a'   |
  4  |  -4 | 'b'   |

Output dataframe: pd.DataFrame.from_dict({"a": [1, 2, 3,4], "b": [-1,-2,-3,-4], "names":['a','b','a','b'], "new_col":[1,-2,3,-4]})

  a  |  b  | names | new_col | 
 --- | --- | ----  | ------  |
  1  |  -1 | 'a'   |    1    |
  2  |  -2 | 'b'   |   -2    |
  3  |  -3 | 'a'   |    3    |
  4  |  -4 | 'b'   |   -4    |

解决方案

You can use lookup:

df['new_col'] = df.lookup(df.index, df.names)
df
#   a    b  names   new_col
#0  1   -1      a   1
#1  2   -2      b   -2
#2  3   -3      a   3
#3  4   -4      b   -4

这篇关于Pandas - 使用其他列值作为列名选择列的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！