#25576: HttpResponse can't be wrapped by io.TextIOWrapper; add required IOBase
methods
-------------------------------+--------------------
Reporter: jdufresne | Owner: nobody
Type: Bug | Status: new
Component: HTTP handling | Version: master
Severity: Normal | Keywords:
Triage Stage: Unreviewed | Has patch: 0
Easy pickings: 0 | UI/UX: 0
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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
--
Ticket URL: <https://code.djangoproject.com/ticket/25576>
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