Keepends param in codec readline(s)

[amccampos]

BPO	8630
Nosy	@malemburg, @benjaminp
Files	codecs.py: new codecs.py fixing the issue Issue8630.patch: Patch to add missing keepends parameters 45139b30afef.diff: Adds missing parameters to readline and readlines. Adds tests to test_codecs.py

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2010-05-05.16:38:14.552>
labels = ['type-bug', 'library']
title = 'Keepends param in codec readline(s)'
updated_at = <Date 2019-03-15.23:41:27.662>
user = 'https://bugs.python.org/amccampos'

bugs.python.org fields:

activity = <Date 2019-03-15.23:41:27.662>
actor = 'BreamoreBoy'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2010-05-05.16:38:14.552>
creator = 'amccampos'
dependencies = []
files = ['17235', '35649', '35729']
hgrepos = ['259']
issue_num = 8630
keywords = ['patch']
message_count = 8.0
messages = ['105056', '105128', '105132', '105133', '105140', '105324', '220668', '221291']
nosy_count = 4.0
nosy_names = ['lemburg', 'benjamin.peterson', 'amccampos', 'jeffrey.falgout']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue8630'
versions = ['Python 2.7', 'Python 3.4', 'Python 3.5']

[amccampos]

Some methods in StreamReaderWriter class (codecs library) has different signatures from StreamReader methods. More precisely it's missing the keepends parameter in readline and readlines methods.

So, we cannot code:
fp = codecs.open(fileName, "r", "utf-8")
lines = fp.readlines(keepends=False)
or
line = fp.readline(keepends=False)

[malemburg]

We can add those to 3.2. Not sure about 2.7 - it's already in feature freeze.

[malemburg]

Benjamin: Would the added parameter be a new feature or not ?

It looks like an oversight when adding the parameter to the standard codec classes, so could be viewed as a bug.

[malemburg]

André: Could you provide a patch ?

Thanks.

[amccampos]

The parameter would not be a new feature since the codecs docs states that:
"The StreamReaderWriter allows wrapping streams which work in both
read and write modes".

The reader (StreamReader) accepts the parameter, so it's expected that
StreamReaderWriter does the same.

I'm not sure how to submit a patch.
So, I'm submitting a new codecs.py file through the issue track
interface (bpo-8630).
If it's not that in that way, could you please tell me the path?
André.

2010/5/6 Marc-Andre Lemburg <report@bugs.python.org>:

Marc-Andre Lemburg <mal@egenix.com> added the comment:

André: Could you provide a patch ?

Thanks.

----------
assignee: benjamin.peterson ->

---

Python tracker <report@bugs.python.org>
<http://bugs.python.org/issue8630\>

---

[benjaminp]

I think this can qualify as a bug fix.

[BreamoreBoy]

As codecs.py has changed I've generated a patch file which adds the missing parameters. I looked at test_codecs.py but could only find one reference to the StreamReaderWriter class in WithStmtTest. I'm sorry but I'll have to leave writing tests for StreamReaderWriter to somebody that's better qualified than myself.

[jeffreyfalgout]

Wrote tests

[bhaible]

I stumbled across this too: I have an input file with contents

This is line 2.



And line 6.

I want to get the contents of this file, as a list of lines, with the trailing newlines removed. There is only one reference to a readlines method in the current documentation, namely at https://docs.python.org/3.12/library/codecs.html#codecs.StreamReader.readlines , and it shows the signature

readlines(sizehint=None, keepends=True)

But I cannot find how to invoke this method with keepends=False:

>>> import codecs

>>> codecs.open('input.txt', 'rb', 'UTF-8').readlines()
['\n', 'This is line 2.\n', '\n', '\n', '\n', 'And line 6.\n', '\n']

>>> codecs.open('input.txt', 'rb', 'UTF-8').readlines(False)
['\n', 'This is line 2.\n', '\n', '\n', '\n', 'And line 6.\n', '\n']

>>> codecs.open('input.txt', 'rb', 'UTF-8').readlines(None,False)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: StreamReaderWriter.readlines() takes from 1 to 2 positional arguments but 3 were given

>>> codecs.open('input.txt', 'rb', 'UTF-8').readlines(keepends=False)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: StreamReaderWriter.readlines() got an unexpected keyword argument 'keepends'

>>> codecs.open('input.txt', 'rb', 'UTF-8').readlines(sizehint=None, keepends=False)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: StreamReaderWriter.readlines() got an unexpected keyword argument 'keepends'