#348 DeprecationWarning: 'U' mode is deprecated

[Hugo]

I'm not using docutils directly, but it's used by a dependency. There will be an easier way to reproduce it, this is how I'm getting it with Python 3.7:

git clone https://github.com/python-pillow/Pillow && cd Pillow
pip install -e .
pip install pyroma
python Tests/test_pyroma.py

Results in:

<snip other warnings>
/usr/local/lib/python3.7/site-packages/docutils/io.py:245: DeprecationWarning: 'U' mode is deprecated
  self.source = open(source_path, mode, **kwargs)
.
----------------------------------------------------------------------
Ran 1 test in 0.520s

OK

It is caused by the U in the mode here:

class FileInput(Input):

    """
    Input for single, simple file-like objects.
    """
    def __init__(self, source=None, source_path=None,
                 encoding=None, error_handler='strict',
                 autoclose=True, mode='rU', **kwargs):

Since Python 3.4, the 'U' universal newlines mode has been deprecated.
https://docs.python.org/3.4/library/functions.html#open

From Python 3.0-3.3, it has been labelled "for backwards compatibility; unneeded for new code".
https://docs.python.org/3.0/library/functions.html#open

[Hugo]

Python 3.7.0
docutils 0.14

Smaller test case:

import pyroma
data = pyroma.projectdata.get_data(".")
rating = pyroma.ratings.rate(data)

And run with deprecation warnings enabled:

$ pip install pyroma
$ python -W default::DeprecationWarning pyroma-test.py
<snip other warnings>
/usr/local/lib/python3.7/site-packages/docutils/io.py:245: DeprecationWarning: 'U' mode is deprecated

[Stéphane Blondon]

It's probably a problem to remove it because docutils still supports python2.

[engelbert gruber]

Shouldn't it then be handled by 2to3 ?

"Stéphane Blondon" stephaneb@users.sourceforge.net schrieb am Sa., 11.
Aug. 2018, 14:50:

It's probably a problem to remove it because docutils still supports
python2.

---

• [bugs:#348] https://sourceforge.net/p/docutils/bugs/348/
  DeprecationWarning: 'U' mode is deprecated*

Status: open
Group: Default
Created: Thu Aug 09, 2018 09:02 AM UTC by Hugo
Last Updated: Thu Aug 09, 2018 09:14 AM UTC
Owner: nobody

I'm not using docutils directly, but it's used by a dependency. There will
be an easier way to reproduce it, this is how I'm getting it with Python
3.7:

git clone https://github.com/python-pillow/Pillow && cd Pillow
pip install -e .
pip install pyroma
python Tests/test_pyroma.py

Results in:

<snip other="" warnings="">
/usr/local/lib/python3.7/site-packages/docutils/io.py:245: DeprecationWarning: 'U' mode is deprecated
self.source = open(source_path, mode, **kwargs)
.</snip>

---

Ran 1 test in 0.520s

OK

It is caused by the U in the mode here:

class FileInput(Input):

"""    Input for single, simple file-like objects.    """
def __init__(self, source=None, source_path=None,
             encoding=None, error_handler='strict',
             autoclose=True, mode='rU', **kwargs):

Since Python 3.4, the 'U' universal newlines mode has been deprecated.
https://docs.python.org/3.4/library/functions.html#open

From Python 3.0-3.3, it has been labelled "for backwards compatibility;
unneeded for new code".
https://docs.python.org/3.0/library/functions.html#open

---

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[Ovidiu Ciule]

2to3 does not have a fixer for this issue, as it was written to fix issues when migrating from py2.x to 3.0 and using the "U" mode started throwing DeprecatedWarning only in 3.4.

It's possible to write a custom fixer, or course.

[Hugo]

Maybe something along the lines of this?

mode = 'r' if sys.version_info >= (3, 4) else 'rU'

[Hugo]

I've created a patch with this suggestion:

https://sourceforge.net/p/docutils/patches/144/

[engelbert gruber]

thanks and all the best