Finding an array elements location in a pandas frame column (a.k.a pd.series)

Question

I have a pandas frame similar to this one:

import pandas as pd
import numpy as np

data = {\'Col1\' : [4,5,6,7], \'Col2\' : [10,20,30,40], \'Col3\' : [100,5         


        

Answer 1

You can use NumPy's in1d -

df.index[np.in1d(df['Col4'],target_array)]

Explanation

1) Create a 1D mask corresponding to each row telling us whether there is a match between col4's element and any element in target_array :

mask = np.in1d(df['Col4'],target_array)

2) Use the mask to select valid indices from the dataframe as final output :

out = df.index[np.in1d(df['Col4'],target_array)]