Pandas apply

I often use Pandas to process NLP data. In many cases I want to create a new column from the information in an existing column. For example, if I want to have the number of characters or tokens.

This can easily be done with the help of the apply function of Pandas.

However, an extreme case is when you want to apply one single function to create two new columns from the information of two existing columns.

Here I show you how it’s done.

import pandas as pd

df = pd.DataFrame(
    {
        "int1": [1, 2, 3],
        "int2": [11, 12, 13],
        "strings": ["string1", "string2", "string3"],
    }
)
df

	int1	int2	strings
0	1	11	string1
1	2	12	string2
2	3	13	string3

def add_and_multiply(x, y):
    add_result = x + y
    multiply_result = x * y
    return add_result, multiply_result

df[["int1_plus_int2", "int1_times_int2"]] = df[["int1", "int2"]].apply(
    lambda x: add_and_multiply(*x),
    axis=1,
    result_type="expand",
)
df

	int1	int2	strings	int1_plus_int2	int1_times_int2
0	1	11	string1	12	11
1	2	12	string2	14	24
2	3	13	string3	16	39

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