How to filter a Pandas Dataframe based on a list and its order.

import pandas as pd

df = pd.DataFrame({'country': ['Italy', 'Greece', 'Japan', 'Germany']})
countries_to_keep = ['Japan', 'Italy']
df

   country
0    Italy
1   Greece
2    Japan
3  Germany

The usual way to filter the Dataframe is by using the ‘isin’ function:

df[df.country.isin(selected_countries)]

  country
0   Italy
2   Japan

Now, If we want to keep the order of the list we can do the following:

ind=[df.index[df['country']==i].tolist() for i in selected_countries]
flat_ind=[item for sublist in ind for item in sublist]

df.reindex(flat_ind)

  country
2   Japan
0   Italy