根据另一个列pandas数据框提取列值 [英] extract column value based on another column pandas dataframe

问题描述

我有点想提取一个变量的值，而条件又是另一个变量.例如，以下数据框:

I am kind of getting stuck on extracting value of one variable conditioning on another variable. For example, the following dataframe:

A  B
p1 1
p1 2
p3 3
p2 4

当B=3时如何获得A的值?每次提取A的值时，我都会得到一个对象，而不是字符串.

How can I get the value of A when B=3? Every time when I extracted the value of A, I got an object, not a string.

推荐答案

您可以使用

You could use loc to get series which satisfying your condition and then iloc to get first element:

In [2]: df
Out[2]:
    A  B
0  p1  1
1  p1  2
2  p3  3
3  p2  4

In [3]: df.loc[df['B'] == 3, 'A']
Out[3]:
2    p3
Name: A, dtype: object

In [4]: df.loc[df['B'] == 3, 'A'].iloc[0]
Out[4]: 'p3'

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