Write column data from csv in to a line / row in a text file

Question

im working in a script to read a .csv file , read an specific column and write it in a txt file, the problem is, that the extracted data is written in a column, in this form:

primary_channel
2
1
0
0
2
0
1
2
1

and i need it in a line,like this:

2,1,0,0,2,0,1,2,1

my code is the next,

import sys
import csv
import copy
import os
import random
import fileinput
import sys, glob
from io import StringIO
from collections import OrderedDict
import sys
#scriptname,f1name,f2name=sys.argv

fieldnames=['node_code;node_type;wlan_code;destination_id;x(m);y(m);z(m);primary_channel;min_channel_allowed;max_channel_allowed;cw;cw_stage;tpc_min(dBm);tpc_default(dBm);tpc_max(dBm);cca_min(dBm);cca_default(dBm);cca_max(dBm);tx_antenna_gain;rx_antenna_gain;channel_bonding_model;modulation_default;central_freq (GHz);lambda;ieee_protocol;traffic_load(pkts/s)']

main={}
with open('nodos_cambiados_1.csv','r') as infile,open('lista.txt','w') as outfile:
     reader = csv.DictReader(infile,delimiter=";" )
     writer = csv.DictWriter(outfile,fieldnames=['primary_channel'],delimiter=",",extrasaction='ignore')
     writer.writeheader()
     for row in reader:
         next(reader) 
         for values in row:
             if row['node_type']=='0' in row:
                main.update({row['primary_channel']:()})

         writer.writerow(row)

I will be very grateful for the help you can give me

Can you be more specific about what the issue is? You're very clearly just writing each row, one after the other. Have you tried combining all the data, and then writing that as a single row? Please see How to Ask, help center. — AMC
– AMC, Commented May 3, 2020 at 1:06

Ami Tavory · Accepted Answer · 2020-05-02 21:00:23Z

1

In the call to DictWriter, try adding newline=''. As the documentation notes:

Any other optional or keyword arguments are passed to the underlying writer instance.

answered May 2, 2020 at 21:00

Ami Tavory

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Comments

Johan Schiff · Accepted Answer · 2020-05-02 21:12:51Z

1

Using DictWriter seems like overcomplicating things, if you just want to write numbers on a row. I think something like this will suffice:

with open('nodos_cambiados_1.csv','r') as infile,open('lista.txt','w') as outfile:
     reader = csv.DictReader(infile,delimiter=';')
     outfile.write(','.join(row.get('primary_channel') for row in reader))

answered May 2, 2020 at 21:12

Johan Schiff

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3 Comments

Ami Tavory Over a year ago

It might be simpler, but it has a downside of loading all values into memory.

Johan Schiff Over a year ago

Yes, and that's a problem if you're parsing an amount of data no sane person ever puts into a CSV.

Ami Tavory Over a year ago

It's a problem whenever the ratio of the size of the file and available memory, is high enough. There might be several processes, several other things being stored in memory. I'm not saying that this solution doesn't have benefits, but it also has drawbacks.

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