Applying function with multiple arguments to create a new pandas column

Question

I want to create a new column in a pandas data frame by applying a function to two existing columns. Following this  answer I've been able to create a new column when I only need one column as an argument:

import pandas as pd

df = pd.DataFrame({"A": [10,20,30], "B": [20, 30, 10]})

def fx(x):

    return x * x

print(df)

df['newcolumn'] = df.A.apply(fx)

print(df)

However, I cannot figure out how to do the same thing when the function requires multiple arguments. For example, how do I create a new column by passing column A and column B to the function below?

def fxy(x, y):

    return x * y

Answer 1

This solves the problem:

df['newcolumn'] = df.A * df.B

You could also do:

def fab(row):

  return row['A'] * row['B']

df['newcolumn'] = df.apply(fab, axis=1)

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