Selecting with complex criteria from pandas.DataFrame

Question

For example I have simple DF:

import pandas as pd
from random import randint

df = pd.DataFrame({\'A\': [randint(1, 9) for x in xrange(10)],
                         


        

Answer 1

Another solution is to use the query method:

import pandas as pd

from random import randint
df = pd.DataFrame({'A': [randint(1, 9) for x in xrange(10)],
                   'B': [randint(1, 9) * 10 for x in xrange(10)],
                   'C': [randint(1, 9) * 100 for x in xrange(10)]})
print df

   A   B    C
0  7  20  300
1  7  80  700
2  4  90  100
3  4  30  900
4  7  80  200
5  7  60  800
6  3  80  900
7  9  40  100
8  6  40  100
9  3  10  600

print df.query('B > 50 and C != 900')

   A   B    C
1  7  80  700
2  4  90  100
4  7  80  200
5  7  60  800

Now if you want to change the returned values in column A you can save their index:

my_query_index = df.query('B > 50 & C != 900').index

....and use .iloc to change them i.e:

df.iloc[my_query_index, 0] = 5000

print df

      A   B    C
0     7  20  300
1  5000  80  700
2  5000  90  100
3     4  30  900
4  5000  80  200
5  5000  60  800
6     3  80  900
7     9  40  100
8     6  40  100
9     3  10  600