Writing to io.BytesIO in csv fails in python3

Question

I am trying to write python 2/3 compatible code to write strings to csv file object. This code:

line_as_list = [line.encode() for line in line_as_list]
write         


        

Answer 1

In Python3 csv.writer expects a file-like object opened in text mode. In Python2, csv.writer expects a file-like object opened in binary mode.

Therefore, in Python3, use io.StringIO, while in Python2 use io.BytesIO:

import io
import csv
import sys
PY3 = sys.version_info[0] == 3

line_as_list = [u'foo', u'bar']
encoding = 'utf-8'

if PY3:
    writer_file =  io.StringIO()
else:
    writer_file =  io.BytesIO()
    line_as_list = [line.encode(encoding) for line in line_as_list]

writer = csv.writer(writer_file, dialect='excel', delimiter=',')
writer.writerow(line_as_list)
content = writer_file.getvalue()

if PY3:
    content = content.encode(encoding)

print(type(content))
print(repr(content))

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In Python3 the code above prints

<class 'bytes'>
b'foo,bar\r\n'

In Python2 the code above prints

<type 'str'>
'foo,bar\r\n'