Printing to a CSV file using Python

Question

I need to print headers and data rows to a CSV file. Here is my code:

import csv

import sys

  with open(r'C:\Users\testuser\Desktop\raw_inpuy.csv','rb') as csvfile:

        reader=csv.reader(csvfile,delimiter=',')
        first=True
        data={}
        for row in reader:
            if first:
                 first= False
                   continue
            if not int(row[1]) in data:
                 data[int(row[1])]=[]
               data[int(row[1])].append(float(row[3]))


    with open (r'C:\Users\testuser\Desktop\outcome.csv','wb') as f_out:
        outwriter=csv.writer(f_out,delimiter=',')
       f_out.write(";".join(['Size','S1','S2','S3','S4']))
       for item in data:
        row=[item]
        row.extend(data[item])
        f_out.write(";".join(map(str,row)))

I get this error:

**ERROR Expected a character buffer obj**

No! you can't just rewrite the question completely based on first answers. rollback, accept an answer and ask another question! — Assem
– Assem, Commented Aug 17, 2015 at 22:11

Assem · Accepted Answer · 2015-08-17 21:55:34Z

3

You should feed writer.write with an str not a list:

 writer.write(";".join(['Size','S1','S2','S3','S4']))

also:

 writer.write(";".join(map(str, row)))

edited Aug 17, 2015 at 21:55

answered Aug 17, 2015 at 21:49

Assem

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2 Comments

royalblue Over a year ago

New error for the last line is: 'sequence item 0: expected string, int found' what I am writing to the csv consists of strings and integers

Assem Over a year ago

try: writer.write(";".join(map(str, row)))

Michael Laszlo · Accepted Answer · 2015-08-17 22:03:25Z

0

Instead of trying to build your own CSV records, let the csv module handle it. Like this:

import csv

data = [[10, 'foo', 'bar', 'blue', 'green'],
        [20, 'bar', 'foo', 'blue', 'green'],
        [30, 'ba', 'bar', 'red', 'white']]

with open (r'C:\Users\testuser\Desktop\outcome.csv','w') as file:
  writer = csv.writer(file)
  writer.writerow(['Size','S1','S2','S3','S4'])
  for row in data:
    writer.writerow(row)

answered Aug 17, 2015 at 22:03

Michael Laszlo

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