Why does CSV file contain a blank line in between each data line when outputting with Dictwriter in Python [duplicate]

Answer 1

Changing the 'w' (write) in this line:

output = csv.DictWriter(open('file3.csv','w'), delimiter=',', fieldnames=headers)

To 'wb' (write binary) fixed this problem for me:

output = csv.DictWriter(open('file3.csv','wb'), delimiter=',', fieldnames=headers)

Python v2.75: Open()

Credit to @dandrejvv for the solution in the comment on the original post above.

Answer 2

From http://docs.python.org/library/csv.html#csv.writer:

If csvfile is a file object, it must be opened with the ‘b’ flag on platforms where that makes a difference.

In other words, when opening the file you pass 'wb' as opposed to 'w'.
You can also use a with statement to close the file when you're done writing to it.
Tested example below:

from __future__ import with_statement # not necessary in newer versions
import csv
headers=['id', 'year', 'activity', 'lineitem', 'datum']
with open('file3.csv','wb') as fou: # note: 'wb' instead of 'w'
    output = csv.DictWriter(fou,delimiter=',',fieldnames=headers)
    output.writerow(dict((fn,fn) for fn in headers))
    output.writerows(rows)

Answer 3

I just tested your snippet, and their is no double spacing line here. The end-of-line are \r\n, so what i would check in your case is:

1. your editor is reading correctly DOS file
2. no \n exist in values of your rows dict.

(Note that even by putting a value with \n, DictWriter automaticly quote the value.)

Answer 4

By default, the classes in the csv module use Windows-style line terminators (\r\n) rather than Unix-style (\n). Could this be what’s causing the apparent double line breaks?

If so, you can override it in the DictWriter constructor:

output = csv.DictWriter(open('file3.csv','w'), delimiter=',', lineterminator='\n', fieldnames=headers)