I want to extract csv file only specific columns in Python, and then cell combine only specific columns in the extracted columns

import polars as pl
import io
csv_file = io.StringIO('''
Email, Last Name, First Name, Birthplace, Address
[email protected] , tanaka, taro, Hokkaido, Tokyo 1-1-1
[email protected] ,sato,hanako,Osaka Prefecture,Kanagawa Prefecture 1-1-2
[email protected] ,takahasi,jiro,Osaka Prefecture,Chiba Prefecture 1-1-3
[email protected],cat,tama,,埼玉県1-1-4
[email protected],dog,pochi,,茨城県1-1-5
''')

df = pl.read_csv(csv_file)
df.select([
    'Email',
    (pl.col('Surname') +' ' +pl.col('First Name')).alias('Surname'),
    'Address',
]).write_csv()

# e-mail, first and last names, address
# # [email protected],tanaka taro,東京都1-1-1
# [email protected] ,satohanako,Kanagawa Prefecture 1-1-2
# # [email protected],takahasi jiro,千葉県1-1-3
# # [email protected],cat tama,埼玉県1-1-4
# # [email protected],dog pochi,茨城県1-1-5

import csv

# "If you want to create a sample file of the original file, run ""~"" as a preparation."
""" 
def create_sample_csv():
    with open("source.csv", "w") as f:
        f.write('email, last name, first name, place of origin, address
[email protected] , tanaka, taro, Hokkaido, Tokyo 1-1-1
[email protected] ,sato,hanako,Osaka Prefecture,Kanagawa Prefecture 1-1-2
[email protected] ,takahasi,jiro,Osaka Prefecture,Chiba Prefecture 1-1-3
[email protected],cat,tama,,埼玉県1-1-4
[email protected],dog,pochi,,茨城県1-1-5
''')

create_sample_csv()
""" 

# Load source.csv to shape and convert required columns into dictionary lists
dicts = [] # Dictionary List
with open("source.csv", "r") as f:
    reader = csv.DictReader(f)
    for row in reader:
        # dictionary row data
        dict = {"Mail": row["Mail"],
                "Surname and First Name": row["Surname"] + " + row["First Name"],
                "Address": row["Address"]}
        dicts.append(dict)

# Output result.csv based on dictionary list
with open("result.csv", "w") as f:
    writer = csv.DictWriter(f, dict.keys(), lineterminator='\n')
    writer.writeheader() # header output
    writer.writerows(dicts) # row data output