Save results to csv file with Python

Question

import csv

with open('test.csv', 'rb') as f:
  data = list(csv.reader(f))

import collections
counter = collections.defaultdict(int)
for row in data:
    counter[row[1]] += 1
for row in data:
    if counter[row[1]] >= 4:
      writer = csv.writer(open("test1.csv", "wb"))
      writer.writerows(row)

I am getting strange output! What is wrong with this code?

Less than 24 hours ago you accepted the [answer that has this link in its content](http://stackoverflow.com/questions/3339403/smallest-learning-curve-language-to-work-with-csv-files/3339430#3339430)! — SilentGhost, Jul 27 '10 at 15:47
I posted this before, but you may not have read it. Seriously, since you're just beginning in Python, it might be a good idea to look through a tutorial and learn the basics of the language, rather than try to learn just the features you need and search for the answers on StackOverflow when you can't find something. It'll take more time, sure, but you'll get a MUCH better understanding of the language. — chimeracoder, Jul 27 '10 at 15:48
See also: [How do I read and write CSV files with Python?](https://stackoverflow.com/q/41585078/562769) — Martin Thoma, Jul 05 '17 at 08:55

Joseph Hansen · Answer 1 · 2019-03-18T20:18:54.393

I know the question is asking about your "csv" package implementation, but for your information, there are options that are much simpler — numpy, for instance.

import numpy as np
np.savetxt('data.csv', (col1_array, col2_array, col3_array), delimiter=',')

(This answer posted 6 years later, for posterity's sake.)

In a different case similar to what you're asking about, say you have two columns like this:

names = ['Player Name', 'Foo', 'Bar']
scores = ['Score', 250, 500]

You could save it like this:

np.savetxt('scores.csv', [p for p in zip(names, scores)], delimiter=',', fmt='%s')

scores.csv would look like this:

Player Name,Score
Foo,250
Bar,500

danben · Accepted Answer · 2010-07-27T16:20:43.317

49

Use csv.writer:

import csv

with open('thefile.csv', 'rb') as f:
  data = list(csv.reader(f))

import collections
counter = collections.defaultdict(int)
for row in data:
    counter[row[0]] += 1


writer = csv.writer(open("/path/to/my/csv/file", 'w'))
for row in data:
    if counter[row[0]] >= 4:
        writer.writerow(row)

edited Jul 27 '10 at 16:20

answered Jul 27 '10 at 15:48

danben

80,905
18
123
145

Squishy · Answer 3 · 2022-08-03T16:34:39.720

8

Use Pandas

   df.to_csv("your_preferred_name.csv")

edited Aug 03 '22 at 16:34

answered Jun 17 '20 at 15:13

Squishy

81
1
5

score 6 · Answer 4 · answered Jan 27 '15 at 12:10

6

You can close files not csv.writer object, it should be:

f = open(fileName, "wb")
writer = csv.writer(f)
String[] entries = "first*second*third".split("*");
writer.writerows(entries)
f.close()

answered Jan 27 '15 at 12:10

Waqas

3,763
1
30
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score 2 · Answer 5 · answered Jul 27 '10 at 15:46

2

An easy example would be something like:

writer = csv.writer(open("filename.csv", "wb"))
String[] entries = "first#second#third".split("#");
writer.writerows(entries)
writer.close()

answered Jul 27 '10 at 15:46

You can close files not csv.writer object, it should be f = open(fileName, "wb") writer = csv.writer(f) String[] entries = "first#second#third".split("#"); writer.writerows(entries) f.close() – Waqas Jan 27 '15 at 12:08

score -1 · Answer 6 · edited Sep 15 '17 at 14:14

-1

This is how I do it

 import csv
    file = open('???.csv', 'r')
    read = csv.reader(file)
    for column in read:
            file = open('???.csv', 'r')
            read = csv.reader(file)
            file.close()
            file = open('????.csv', 'a', newline='')
            write = csv.writer(file, delimiter = ",")
            write.writerow((, ))
            file.close()

edited Sep 15 '17 at 14:14

Verv

2,385
2
23
37

answered Sep 15 '17 at 13:59

Python lover

9

The indentation is incorrect and why do you open the same file twice? – jhoepken Sep 15 '17 at 14:25

score -3 · Answer 7 · edited Apr 20 '18 at 06:43

-3

this will provide exact output

import csv

import collections

with open('file.csv', 'rb') as f:

  data = list(csv.reader(f))

counter = collections.defaultdict(int)

for row in data:

    counter[row[0]] += 1

writer = csv.writer(open("file1.csv", 'w'))

for row in data:

    if counter[row[0]] >= 1:

        writer.writerow(row)

edited Apr 20 '18 at 06:43

Yuankun

6,875
3
32
34

answered Apr 20 '18 at 05:34

kiran

9
1

3

This is just an exact copy of the accepted answer, but with no explanation and no formatting. – DaveyDaveDave Apr 20 '18 at 06:04

Save results to csv file with Python

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