How to filter dataframe with multiple boolean conditions

Question

I need to filter a pandas dataframe with two boolean queries, means I want to keep the ones which are True

dataframe:

import numpy as np

df = pd.DataFrame(np.array([[1, 2, 3], [4, 5, 6], [7, 8, 9]]),
                   columns=['a', 'b', 'c'])

output:

   a  b  c
0  1  2  3
1  4  5  6
2  7  8  9

single filter works:

filter = (df.b == 2) 
df = df[filter]

output:

   a  b  c
0  1  2  3

But how can I filter with df.b == 2 or df.b == 5 ?

I tried:

filter = [(df['b']==2) | (df['b']==5)]
df = df[filter]
print(df)

I get :

ValueError: Item wrong length 1 instead of 3

Any suggestions how do achive it?
my desired output is:

   a  b  c
0  1  2  3
1  4  5  6

Answer 1

You pass list as filter, try this: (better don't use filter as variable, it is built-in function in python)

mask = ((df['b']==2) | (df['b']==5))
df = df[mask]

You can use .inin() as alternative solution like below:

mask = [2,5]
df = df[df['b'].isin(mask)]