Incompatible version is released to Python 2

chainer>=7.0.0 released before #8517 is still released to Python 2, even though they doesn’t support Python 2. Due to this, we cannot use pip install chainer in Python 2. Instead, we always have to specify install version like pip install chainer<7.0.0.

$ pip install --user chainer --no-cache-dir -U
/usr/local/lib/python2.7/dist-packages/pip/_vendor/requests/__init__.py:83: RequestsDependencyWarning: Old version of cryptography ([1, 2, 3]) may cause slowdown.
  warnings.warn(warning, RequestsDependencyWarning)
DEPRECATION: Python 2.7 will reach the end of its life on January 1st, 2020. Please upgrade your Python as Python 2.7 won't be maintained after that date. A future version of pip will drop support for Python 2.7. More details about Python 2 support in pip, can be found at https://pip.pypa.io/en/latest/development/release-process/#python-2-support
Collecting chainer
  Downloading https://files.pythonhosted.org/packages/a8/ba/32b704e077cb24b4d85260512a5af903e772f06fb58e716301dd51758869/chainer-7.0.0.tar.gz (1.0MB)
     |████████████████████████████████| 1.0MB 8.1MB/s 
Requirement already satisfied, skipping upgrade: setuptools in /usr/lib/python2.7/dist-packages (from chainer) (20.7.0)
Requirement already satisfied, skipping upgrade: typing_extensions in /usr/local/lib/python2.7/dist-packages (from chainer) (3.6.6)
Requirement already satisfied, skipping upgrade: filelock in /usr/local/lib/python2.7/dist-packages (from chainer) (3.0.12)
Requirement already satisfied, skipping upgrade: numpy>=1.9.0 in /usr/lib/python2.7/dist-packages (from chainer) (1.11.0)
Requirement already satisfied, skipping upgrade: protobuf>=3.0.0 in /usr/local/lib/python2.7/dist-packages (from chainer) (3.7.1)
Requirement already satisfied, skipping upgrade: six>=1.9.0 in /usr/local/lib/python2.7/dist-packages (from chainer) (1.12.0)
Requirement already satisfied, skipping upgrade: typing>=3.6.2 in /usr/local/lib/python2.7/dist-packages (from typing_extensions->chainer) (3.6.6)
Building wheels for collected packages: chainer
  Building wheel for chainer (setup.py) ... done
  Created wheel for chainer: filename=chainer-7.0.0-cp27-none-any.whl size=966689 sha256=5d7d792512b88770a53c52e193fd05d6d1e3d978e4c7e8f6dcd1abc6980ea5ed
  Stored in directory: /tmp/pip-ephem-wheel-cache-MwgxDb/wheels/42/ab/c8/d723d9d7a08b5649c7343f113e74c729d4a1bd5d96e349294b
Successfully built chainer
Installing collected packages: chainer
Successfully installed chainer-7.0.0
WARNING: You are using pip version 19.2.3, however version 20.0.2 is available.
You should consider upgrading via the 'pip install --upgrade pip' command.
$ python -c 'import chainer'
Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/home/pazeshun/.local/lib/python2.7/site-packages/chainer/__init__.py", line 10, in <module>
    from chainer import backends  # NOQA
  File "/home/pazeshun/.local/lib/python2.7/site-packages/chainer/backends/__init__.py", line 1, in <module>
    from chainer.backends import cuda  # NOQA
  File "/home/pazeshun/.local/lib/python2.7/site-packages/chainer/backends/cuda.py", line 77
    def shape(self) -> types.Shape:
                    ^
SyntaxError: invalid syntax

This situation easily causes mistakes of installing incompatible versions. In addition, this is problem when using ROS. In ROS, we want to resolve all dependency with rosdep install command, but its philosophy is like apt and it doesn’t have a method to specify install version. http://wiki.ros.org/ROS/Tutorials/rosdep (Now we are working on making exceptions of Python packages in that philosophy, but the discussion doesn’t advance: https://github.com/ros-infrastructure/rosdep/pull/694)

I know released version cannot be overwritten, https://stackoverflow.com/questions/21064581/how-to-overwrite-pypi-package-when-doing-upload-from-command-line so solutions I know are the following:

• Release Python 2 compatible version to chainer>=7.0.0 (very strange solution)
• Remove chainer>=7.0.0 released before #8517 (very drastic solution)

I know this is difficult problem, but hope this is solved.

cf. https://github.com/chainer/chainer/pull/8517#issuecomment-576128957

[knorth55]

I checked with pip 20.3.3 and it correctly install 6.7.0 for python2! Thank you so much!

[knorth55][melodic-p50][~]
$ sudo pip install chainer
DEPRECATION: Python 2.7 reached the end of its life on January 1st, 2020. Please upgrade your Python as Python 2.7 is no longer maintained. pip 21.0 will drop support for Python 2.7 in January 2021. More details about Python 2 support in pip can be found at https://pip.pypa.io/en/latest/development/release-process/#python-2-support pip 21.0 will remove support for this functionality.
WARNING: The directory '/home/knorth55/.cache/pip' or its parent directory is not owned or is not writable by the current user. The cache has been disabled. Check the permissions and owner of that directory. If executing pip with sudo, you may want sudo's -H flag.
Collecting chainer
  Downloading chainer-6.7.0.tar.gz (876 kB)
     |████████████████████████████████| 876 kB 8.3 MB/s
Requirement already satisfied: setuptools in /usr/local/lib/python2.7/dist-packages (from chainer) (44.1.1)
Requirement already satisfied: typing<=3.6.6 in /usr/local/lib/python2.7/dist-packages (from chainer) (3.6.6)
Requirement already satisfied: typing_extensions<=3.6.6 in /usr/local/lib/python2.7/dist-packages (from chainer) (3.6.6)
Requirement already satisfied: filelock in ./.local/lib/python2.7/site-packages (from chainer) (3.0.12)
Requirement already satisfied: numpy>=1.9.0 in ./.local/lib/python2.7/site-packages (from chainer) (1.16.6)
Requirement already satisfied: protobuf>=3.0.0 in /usr/local/lib/python2.7/dist-packages (from chainer) (3.14.0)
Requirement already satisfied: six>=1.9.0 in ./.local/lib/python2.7/site-packages (from chainer) (1.15.0)
Building wheels for collected packages: chainer
  Building wheel for chainer (setup.py) ... done
  Created wheel for chainer: filename=chainer-6.7.0-py2-none-any.whl size=885949 sha256=7f3777ae2f0a8a8df8601251eeb9e58725b81259fce41fbdbfbc722555d83a4d
  Stored in directory: /tmp/pip-ephem-wheel-cache-OXXzyg/wheels/2a/79/8c/a36c747a259e068df041501f6101135c04edb121df2876499e
Successfully built chainer
Installing collected packages: chainer
Successfully installed chainer-6.7.0
[knorth55][melodic-p50][~]
$ pip --version
pip 20.3.3 from /usr/local/lib/python2.7/dist-packages/pip (python 2.7)

[kmaehashi]

@pazeshun Thanks for the feedback! As for cupy-cuda* packages, I think it’s reasonable to simply remove Python 2.7 wheels from PyPI, but unfortunately for cupy sdist package I would like to avoid releasing post releases for v7 series which is no longer maintained.