CODEWITHSUNDEEP
pythoncsv
Brian Powell
Brian Powell

Reputation: 3411

How to add a custom column with csv.writer

I have a python script that takes a huge file and copies out only the few columns that I want while also writing a new custom header in the new file.

import csv,time,string,os, requests

og_file = "\\\\network\\x\\test.csv"
today = time.strftime("%Y-%m-%d")


#fields to keep from original file
fields = ["As Of Date", "Ph", "Home Country"]

with open(og_file) as infile, open("c:\\upload\\output_" + today + ".csv", "wb") as outfile:
    r = csv.DictReader(infile)
    w = csv.DictWriter(outfile, fields, extrasaction="ignore")

    wtr = csv.writer( outfile )    
    wtr.writerow(["upload_date", "phone", "country"])
    for row in r:
        w.writerow(row)

As I write this file, I need to create an additional column at the beginning of each row with a number, starting at 1 and going to n, so the output looks like this:

id |    upload_date    |    phone    |   country
1        2012-01-01         555-1234      USA
2        2012-02-01         555-1235      USA
3        2012-03-01         555-1236      USA
4        2012-04-01         555-1237      USA

I'm not sure how I would go about that.

Upvotes: 0

Views: 547

Answers (2)

galaxyan
galaxyan

Reputation: 6111

fields = ["id"] + fields  # so it'll write later

with open(og_file) as infile, open("c:\\upload\\output_" + today + ".csv", "wb") as outfile:
    r = csv.DictReader(infile)
    w = csv.DictWriter(outfile, fields, extrasaction="ignore")

    wtr = csv.writer( outfile )    
    wtr.writerow(["id","upload_date", "phone", "country"])
    for i,row in enumerate(r, start=1):
        row["id"] = i
        w.writerow(row)

Upvotes: 1

Moses Koledoye
Moses Koledoye

Reputation: 78546

You can use a itertools.count object for the id column:

from itertools import count

with open(og_file) as infile, open("c:\\upload\\output_" + today + ".csv", "wb") as outfile:
    r = csv.DictReader(infile)
    w = csv.DictWriter(outfile, fields, extrasaction="ignore")

    wtr = csv.writer( outfile )    
    wtr.writerow(["id", "upload_date", "phone", "country"])
    c = count(1)
    for row in r:
        row['id'] = next(c)
        w.writerow(row)

Upvotes: 1

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