Filter With Value Comparison

import numpy as np
import pandas as pd
df = pd.read_csv('abc.csv')
df
student language science maths history
0 kumar 90 56 34 34
1 kevin 10 34 32 67
2 sammy 90 23 12 32
3 janice 20 67 90 45
4 peter 30 56 45 65
5 prem 90 45 45 34
6 carrol 50 90 45 23 
below_40 = df[df['science'] < 40]
below_40
student language science maths history
1 kevin 10 34 32 67
2 sammy 90 23 12 32