updating on a csv file using python

Question

I am working on a small project,where one of the step is to write on a csv file a list of data. I am looping through a list,and fetching specific data and writing it to a csv. The problem is when the write operation is being processed it removes previous entries of the csv file.My csv writing method is as follows: and an example

def csv_writer(data_list,file_path):
    import csv
    file_p = open(file_path, "wb")
    write_pattern = csv.writer(file_p, delimiter=",", quotechar=",")
    write_pattern.writerow(data_list)
    file_p.close()

An example data list is:

data_list = ['a', '', 'a', 'a', 'd', 'e']

And I am trying to have data in the file as follows:

a,,a,d,e
a,b,c,d,e
a,g.j,l,m

Thanks in advance.

Python documentation to the rescue! docs.python.org/library/functions.html#open — jathanism
– jathanism, Commented Apr 27, 2011 at 17:15
Please, rephrase your sentence in order that it is understandable: " my goal is to every data_list that is returned from the loop" From your exemple, I understand that you want to insert data_list BEFORE all the content of the file. If not so, it means that you will have to do efforts to express your questions in understandable way — eyquem
– eyquem, Commented Apr 27, 2011 at 17:50
@eyquem I have changed it,hope it express the problem well :) — mushfiq
– mushfiq, Commented Apr 27, 2011 at 17:53
No, there is still ambiguity if the exemple means that you want to insert data_list BEFORE or AFTER the existing content — eyquem
– eyquem, Commented Apr 27, 2011 at 17:58

samplebias · Accepted Answer · 2011-04-27 17:14:03Z

5

Maybe open the file in append mode?

file_p = open(file_path, "ab")

answered Apr 27, 2011 at 17:14

samplebias

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1 Comment

mushfiq Over a year ago

it works!thanks alot,I was searching for this mode but unfortunately missed it, at last thought,I will have to custom method for this stuff.

Chris Eberle · Accepted Answer · 2011-04-27 17:15:29Z

0

When you open the file, try opening it for appending, like this.

def csv_writer(data_list,file_path):
    import csv
    file_p = open(file_path, "a")
    write_pattern = csv.writer(file_p, delimiter=",", quotechar=",")
    write_pattern.writerow(data_list)
    file_p.close()

answered Apr 27, 2011 at 17:15

Chris Eberle

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Comments

eyquem · Accepted Answer · 2011-04-27 17:52:49Z

0

delimiter and quotechar must preferably be choosen as different

As I understood the question, the aim is to insert a new line before all the content of a CSV file. Here's the code to do that:

import csv

def csv_writer(data_list,file_path):
    file_p = open(file_path, "rb+")
    reader_pattern = csv.reader(file_p, delimiter=",", quotechar="$")
    write_pattern = csv.writer(file_p, delimiter=",", quotechar="$")

    content = list(reader_pattern)

    file_p.seek(0,0)
    write_pattern.writerow(data_list)
    write_pattern.writerows(content)
    file_p.truncate()
    file_p.close()


data_list = ['a', '', 'a', 'a', 'd', 'e']


csv_writer(data_list,'Copie de zozou.txt')

edited Apr 27, 2011 at 17:52

answered Apr 27, 2011 at 17:23

eyquem

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