How to save dataframe after generating with a custom function (python)

April 5, 2022

I have a custom function that generates a new column based on an equation, but I cannot see col3 after running the function and printing out the dataframe.

How can I get the new column to save as a pandas dataframe?

Here is what I have done thus far:

#Import modules
import pandas as pd
import numpy as np

#Define the custom function
def example(a, b, c):
    """
    Example function, generates a new column based on user inputs
    """
    
    #Generate input dataframe
    d = {
    'col1': [1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1],
    'col2': [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20]
    }

    dataframe = pd.DataFrame(data=d)
    
    #Create a new column based on an equation
    dataframe['col3'] = dataframe['col1'] * a * b * c
    
    return dataframe

Calling the function…

example(2, 4, 6)

…gives this output:

    col1 col2 col3
0   1   1   48
1   1   2   48
2   1   3   48
3   1   4   48
4   1   5   48
5   1   6   48
6   1   7   48
7   1   8   48
8   1   9   48
9   1   10  48
10  1   11  48
11  1   12  48
12  1   13  48
13  1   14  48
14  1   15  48
15  1   16  48
16  1   17  48
17  1   18  48
18  1   19  48
19  1   20  48

However, printing the dataframe shows that the column hasn’t been added:

dataframe

An error message is generated:

---------------------------------------------------------------------------
NameError                                 Traceback (most recent call last)
Input In [4], in <cell line: 1>()
----> 1 dataframe

NameError: name 'dataframe' is not defined

How can I fix this so that col3 is appended onto the original dataframe?