append new row to old csv file python

append new row to old csv file python

with open(document.csv,a) as fd:
    fd.write(myCsvRow)

Opening a file with the a parameter allows you to append to the end of the file instead of simply overwriting the existing content. Try that.

I prefer this solution using the csv module from the standard library and the with statement to avoid leaving the file open.

The key point is using a for appending when you open the file.

import csv   
fields=[first,second,third]
with open(rname, a) as f:
    writer = csv.writer(f)
    writer.writerow(fields)

If you are using Python 2.7 you may experience superfluous new lines in Windows. You can try to avoid them using ab instead of a this will, however, cause you TypeError: a bytes-like object is required, not str in python and CSV in Python 3.6. Adding the newline=, as Natacha suggests, will cause you a backward incompatibility between Python 2 and 3.

append new row to old csv file python

Based in the answer of @G M and paying attention to the @John La Rooys warning, I was able to append a new row opening the file in amode.

Even in windows, in order to avoid the newline problem, you must declare it as newline=.

Now you can open the file in amode (without the b).

import csv

with open(rnames.csv, a, newline=) as csvfile:
    fieldnames = [This,aNew]
    writer = csv.DictWriter(csvfile, fieldnames=fieldnames)

    writer.writerow({This:is, aNew:Row})

I didnt try with the regular writer (without the Dict), but I think that itll be ok too.