How to move selected data from one column to another in python

Question

I'm reading a CSV file that have two columns: continent, countries. The cells are empty under each continents.

Continent    |  Countries
-----------------------------
    Asia       |   China
               |   Japan
               |   Korea
    North Am.  |   Canada
               |   U.S.

but I would like to merge these two columns under Continent column and have an indentation.

Continent
-----------
Asia 
    China
    Japan
    Korea
North America
    Canada
    U.S.

How can I do this using python?

Answer 1

The code below should do the trick. You don't even need to use pandas to read a CSV as Python have already a standard module for that called csv . The code outputs to another CSV called output.csv .

import csv

continent = ''
with open('data.csv') as csv_in, open('output.csv', 'w') as csv_out:
    reader = csv.reader(csv_in)
    writer = csv.writer(csv_out)
    headers = next(reader, None) # skip the headers
    writer.writerow([headers[0]])
    for row in reader:
        prev_continent = continent
        continent = row[0].strip() or continent

        if prev_continent != continent:
          writer.writerow([continent])
        writer.writerow([f'    {row[1]}'])

output.csv

Continent
Asia
    China
    Japan
    Korea
North Am.
    Canada
    U.S.

data.csv

Continent,Countries
Asia     ,China
         ,Japan
         ,Korea
North Am.,Canada
         ,U.S.