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?
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Answer
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