How can I apply a function to each row in a DataFrame?

How can I apply a function to each row in a DataFrame?

You can use the apply method in pandas. For example, df.apply(your_function, axis=1) applies the function to each row.

Can you show me an example with a custom function?

Sure! Here's a simple example:

import pandas as pd

def my_function(row):
    return row['A'] + row['B']

df['C'] = df.apply(my_function, axis=1)

This adds columns 'A' and 'B' and stores the result in column 'C'.

What if I want to apply a lambda function instead?

You can use a lambda function directly in the apply method like this:

df['C'] = df.apply(lambda row: row['A'] + row['B'], axis=1)

Are there any performance considerations when using apply?

Yes, using apply can be slower than vectorized operations. If possible, try to use built-in pandas functions for better performance.