CODEWITHSUNDEEP
pythoncsv
Terry Welch
Terry Welch

Reputation: 1

Python 2.7 - Edit Specific Row,Column in CSV

I have a CSV with a bunch of data, and I need to change the data in a specific row and column. I'm able to read through the file, find the row,col that I need to change, change the data, but I can't figure out how to commit that change to memory and re-write the CSV correctly.

The following code does not fail, however it is not correct. Instead of committing the changes that I make to the column (col), it just duplicates the row that I want to change. The data is unchanged, and now I just have duplicate rows where I wanted changes.

import csv
import re
from tempfile import NamedTemporaryFile
import shutil

csvName = raw_input("Enter the filename: ")
tempfile = NamedTemporaryFile(delete=False)
newSize = 0
newArea = 0

with open(csvName, 'rb') as readCSV, tempfile:
    reader = csv.reader(readCSV)
    writer = csv.writer(tempfile)
    for row in reader:
        for col in row:
            if col.startswith('Connection:'):
                print col
            if col.startswith('Size:'):
                print "Current", col
                newSize = raw_input("Enter new size: ")
                newArea = int(newSize)*int(newSize)
                col = re.sub('[0-9]+', newSize, col)
                writer.writerow(row)
            if col.startswith('Area:'):
                col = re.sub('[0-9]+', str(newArea), col)
                writer.writerow(row)
        writer.writerow(row)

shutil.move(tempfile.name, csvName)

This is an example of one bit of data that needs to be changed:

Connection: D14Conn Type: B2B Size: 140 Geometry: Square Area: 19600

My code above will simply duplicate new rows into this data, and the changes I make to col are not committed - as below

Connection: D14Conn Type: B2B Size: 140 Size: 140 Geometry: Square Area: 19600 Area: 19600

Upvotes: 0

Views: 544

Answers (2)

Chris Kenyon
Chris Kenyon

Reputation: 218

When you assign to col you are assigning to a copy of the col value in row. As you iterate through row, you need to either keep reference to the index of the value you want to change, and update row at that index so that when you call writer.writerow(row) you are actually writing with a changed object, or create a new_row with the desired columns. As for your duplicates, remove writer.writerow(row) calls from your if blocks, they are redundant.

Upvotes: 1

wendykan
wendykan

Reputation: 1

Your row isn't changed. You need to make a new_row with your new column values and do writer.writerow(new_row)

Upvotes: 0

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