check if all element of a column of a pandas dataframe are equal to a particular value

gabboshow 0
Viewed 16

Hello given a dataframe I would like to check that all the values of a particular column are equal to 9.

import pandas as pd
import numpy as np

df = pd.DataFrame(data=[[1,2],[2,9],[np.nan,9],[3,9]],columns=['A','B'])

df
        A   B
    0   1.0 2
    1   2.0 9
    2   NaN 9
    3   3.0 9

My solution would be:

if ((df.loc[:,"B"].unique()==[9]).all()):
     ...

Is there a better way to do so?

pandas python
1 Answers

Use DataFrame.all with compare by Series.eq:

if df.B.eq(9).all():
    print ('all values are 9')

EDIT: Like mentioned @mozway use:

assert df.B.eq(9).all()
#AssertionError

With custom error:

if df.B.ne(9).any():
    raise Exception('All values in column are not equal 9')
    
Exception: All values in column are not equal 9
jezrael0
Related