Python 3.1.3 Win 7: csv writerow Error "must be bytes or buffer, not str"

Question

Got a simple script which worked perfectly under Python 2.7.1 at my Win xp machine. Now got a win 7 machine with python 3.1.3.

The code is:

owriter.writerow(dtime[1][1])

dtime[1][1]=['30-Aug-10 16:00:00', '2.5', '15']

Got this error message: TypeError: must be bytes or buffer, not str

What changes should I make?

thanks.

Answer 1

Probably you need to open the file in text mode. If not, include enough of your code so it's runnable and demonstrates the problem.

Answer 2

In Python 2.X, it was required to open the csvfile with 'b' because the csv module does its own line termination handling.

In Python 3.X, the csv module still does its own line termination handling, but still needs to know an encoding for Unicode strings. The correct way to open a csv file for writing is:

outputfile=open("out.csv",'w',encoding='utf8',newline='')

encoding can be whatever you require, but newline='' suppresses text mode newline handling. On Windows, failing to do this will write \r\r\n file line endings instead of the correct \r\n. This is mentioned in the 3.X csv.reader documentation only, but csv.writer requires it as well.