Python Edit CSV headers

Question

I have the following data from a csv file called temp.

Item,Description,Base Price,Available
2000-000-000-300,AC - CF/M Series Green For Black Hood,299.99,3
2000-000-000-380,AC - CF/M Series Green For White Hood,299.99,3

I need to change the headers to read

Item Number,Item Description,List Price,QTY Available

I have been searching similar questions on here and haven't a solution that I can understand since I am relatively new to python programming. So far I have:

import csv
import os

inputFileName = "temp.csv"
outputFileName = os.path.splitext(inputFileName)[0] + "_modified.csv"

with open(inputFileName) as inFile, open(outputFileName, "w") as outfile:
    r = csv.reader(inFile)
    w = csv.writer(outfile)

Which I know only reads the original file and then will write to _modified. How do I select the current headers and then change them so that they write to the new file?

Martijn Pieters · Accepted Answer · 2013-04-30 19:10:43Z

18

The headers are just another row of CSV data. Just write them as a new row to the output followed by the rest of the data from the input file.

import csv
import os

inputFileName = "temp.csv"
outputFileName = os.path.splitext(inputFileName)[0] + "_modified.csv"

with open(inputFileName, 'rb') as inFile, open(outputFileName, 'wb') as outfile:
    r = csv.reader(inFile)
    w = csv.writer(outfile)

    next(r, None)  # skip the first row from the reader, the old header
    # write new header
    w.writerow(['Item Number', 'Item Description', 'List Price', 'QTY Available'])

    # copy the rest
    for row in r:
        w.writerow(row)

For Python 3, use:

with open(inputFileName, newline='') as inFile, open(outputFileName, 'w', newline='') as outfile:

and you may have to specify an encoding for your data.

edited Apr 30, 2013 at 19:10

answered Apr 30, 2013 at 18:44

Martijn Pieters

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12 Comments

John Y Over a year ago

The usual way to call next in Python 3 is next(r) (one parameter). For those who are using Python 2, it would be r.next(). (I can deduce from OP's comment that he didn't have a problem with your next invocation, though. ;)

John Y Over a year ago

@barkl3y: Yeah, group all the arguments into a single list or tuple first. (Just put a pair of square brackets or a second set of parens around the arguments.)

Martijn Pieters Over a year ago

@JohnY: next() takes a default. If r is empty, next(r) throws StopIteration, while next(r, None) returns the default None instead.

Martijn Pieters Over a year ago

@JohnY: and next() works great in Python 2 as well. By using next() your code becomes compatible between Python 2 and 3. In Python 3 you could also call r.__next__() but using next() is more pythonic.

John Y Over a year ago

Ah, old habit. next() was introduced in Python 2.6, and one of the platforms I use Python on was stuck at 2.3.3 until only recently.

|

Hai Vu · Accepted Answer · 2013-04-30 19:09:52Z

1

Another solution is to use the fileinput module to update the file in place:

import fileinput
for line in fileinput.input('temp', inplace=True):
    if fileinput.isfirstline():
        print 'Item Number,Item Description,List Price,QTY Available'
    else:
        print line,

answered Apr 30, 2013 at 19:09

Hai Vu

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Comments

unutbu · Accepted Answer · 2013-04-30 18:53:59Z

0

You could use fileinput for this:

import fileinput
import sys
import os

inputFileName = "temp.csv"
outputFileName = os.path.splitext(inputFileName)[0] + "_modified.csv"

with open(outputFileName, "w") as outfile:
    for line in fileinput.input(
        [inputFileName],
        inplace=False):
        if fileinput.isfirstline():
            outfile.write('Item Number,Item Description,List Price,QTY Available\n')
        else:
            outfile.write(line)

edited Apr 30, 2013 at 18:53

answered Apr 30, 2013 at 18:48

unutbu

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