CSV write error on Python 3

Question

I am trying to save output from a module to CSV file and I got an error when I ran the following code, which is a part of a module:

base_keys = ['path', 'rDATE', 'cDate', 'cik', 'risk', 'word_count']
outFile = open('c:\\Users\\ahn_133\\Desktop\\Python Project\\MinkAhn_completed2.csv','wb')
dWriter = csv.DictWriter(outFile, fieldnames=base_keys)
dWriter.writerow(headerDict)

Here is the error message (base_keys are the headings.)

return self.writer.writerow(self._dict_to_list(rowdict))
TypeError: 'str' does not support the buffer interface

I dont' even understand what the error message is about. I use Python 3.3 and Windows 7.

Thanks for your time.

Show more of your code, especially the definition of _dict_to_list. — Ned Batchelder
– Ned Batchelder, Commented Dec 9, 2012 at 17:48
Python3 uses bytes instead of strings in many cases where encoding comes into play. Try encoding/decoding where appropriate. — Waleed Khan
– Waleed Khan, Commented Dec 9, 2012 at 17:49
Then I'll give you the First Rule of Debugging: When In Doubt, Print More Out. What value is _dict_to_list returning? If it's well-named, it's a list, but maybe it isn't. — Ned Batchelder
– Ned Batchelder, Commented Dec 9, 2012 at 18:04

Lennart Regebro · Accepted Answer · 2012-12-10 09:50:54Z

6

Opening a file in binary mode to write csv data to doesn't work in Python 3, simply put. What you want is to open in text mode and either use the default encoding or specify one yourself, i.e., your code should be written like:

import csv
k = ['hi']
out = open('bleh.csv', 'w', newline='', encoding='utf8') # mode could be 'wt' for extra-clarity
writer = csv.DictWriter(out, k)
writer.writerow({'hi': 'hey'})

Now, due to a bug, you also need to specify newline='' when opening this file for writing the CSV output.

edited Dec 10, 2012 at 9:50

Lennart Regebro

173k45 gold badges230 silver badges254 bronze badges

answered Dec 9, 2012 at 18:20

mmgp

19.3k3 gold badges56 silver badges80 bronze badges

Sign up to request clarification or add additional context in comments.

4 Comments

jfs Over a year ago

the bug was about code examples for csv.writer in csv docs lacking newline='' in Python 3. The bug is not the cause.

mmgp Over a year ago

I'm not following you @J.F.Sebastian, are you implying that newline='' doesn't affect Python 3, or that it doesn't affect when using csv.DicWriter, or something else ? This certainly wasn't the problem in OP's code because he couldn't even write to the file (because he opened in binary mode), but it would be the next bug.

jfs Over a year ago

look at the patch that fixes the bug. It is a documentation bug, no code in cvs is changed due to this bug. Your answer implies that there is some bug in csv module itself (the code).

mmgp Over a year ago

I've seen it. While my answer never said it was a bug in the code (and only that it was a bug) we can get into this new argument. But I'm not seeing the importance of discussing this.

Collectives™ on Stack Overflow

CSV write error on Python 3

1 Answer 1

4 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

4 Comments

Your Answer

Sign up or log in

Post as a guest

Related