id	summary	reporter	owner	description	type	status	component	version	severity	resolution	keywords	cc	stage	has_patch	needs_docs	needs_tests	needs_better_patch	easy	ui_ux
25576	HttpResponse can't be wrapped by io.TextIOWrapper; add required IOBase methods	Jon Dufresne	nobody	"In Python3, the stdlib CSV writer [1] is expected to write to a text file, not a binary file. Observe writing to a bytes buffer:

{{{
import io
import csv

b = io.BytesIO()
w = csv.writer(b)
w.writerow(['a', 'b', 'c'])
}}}

{{{
Traceback (most recent call last):
  File ""test.py"", line 8, in <module>
    w.writerow(['a', 'b', 'c'])
TypeError: 'str' does not support the buffer interface
}}}

To handle this, one should use the stdlib's {{{io.TextIOWrapper}}} [2]:

{{{
import io
import csv

b = io.BytesIO()
wrapper = io.TextIOWrapper(b, 'utf-8', newline='')
w = csv.writer(wrapper)
w.writerow(['a', 'b', 'c'])
wrapper.flush()
print(b.getvalue())
}}}

{{{
b'a,b,c\r\n'
}}}

As Django's HttpResponse uses a binary file-like interface, I'd expect the same to work. That is, wrap the response in a {{{io.TextIOWrapper}}} and write the CSV document to the wrapper. However, this fails:

{{{
import io
import csv
from django.http.response import HttpResponse

r = HttpResponse()
wrapper = io.TextIOWrapper(r, 'utf-8', newline='')
w = csv.writer(wrapper)
w.writerow(['a', 'b', 'c'])
wrapper.flush()
print(r)
}}}

{{{
Traceback (most recent call last):
  File ""/home/jon/test.py"", line 8, in <module>
    wrapper = io.TextIOWrapper(r, 'utf-8')
AttributeError: 'HttpResponse' object has no attribute 'readable'
}}}

As HttpResponse is a binary file-like interface, I'm suggesting the necessary methods/members be added so that it can be wrapped by {{{io.TextIOWrapper}}}. These methods/members are documented in io.BaseIO() [3]. From initial testing, only {{{readable()}}} and {{{seekable()}}} are required for my use case.

This will make it easier to integrate text-only file interfaces to the binary nature of the response.

[1] https://docs.python.org/3/library/csv.html#csv.writer
[2] https://docs.python.org/3/library/io.html#io.TextIOWrapper
[3] https://docs.python.org/3/library/io.html#io.IOBase
"	New feature	closed	HTTP handling	dev	Normal	fixed			Ready for checkin	1	0	0	0	0	0