extract column value based on another column pandas dataframe

Question

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

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.

Answer 1

To get the series that satisfy our condition use loc and then to get the first element use iloc:

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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