Python pandas - new column's value if the item is in the list

12,306

Use isin for check membership:

df1["EU"] = np.where(df1["Country"].isin(EU), "EU", "Other")
print (df1)
      Capital  Country     EU
0  Washington      USA  Other
1      Berlin  Germany     EU
2      Moscow   Russia  Other
3      Warsaw   Poland     EU
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Roberto
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Roberto

Updated on June 07, 2022

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  • Roberto
    Roberto almost 2 years

    I want to create a new column in pandas dataframe. The first column contains names of countries. The list contains countries I am interested in (eg. in EU). The new colum should indicate if country from dataframe is in the list or not.

    Below is the shortened version of the code:

    import pandas as pd
    import numpy as np
    
    EU = ["Austria","Belgium","Germany"]
    
    df1 = pd.DataFrame(data={"Country":["USA","Germany","Russia","Poland"], "Capital":["Washington","Berlin","Moscow","Warsaw"]})
    
    df1["EU"] = np.where(df1["Country"] in EU, "EU", "Other")
    

    The error I get is:

    ValueError: The truth value of a Series is ambiguous. Use a.empty, a.bool(), a.item(), a.any() or a.all().

    I don't know what the problem is and how to solve it. What am I missing?