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Pyenv Fails To Install Python On Cygwin: Modulenotfounderror: No Module Named '_ctypes'

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I am trying to set up my Cygwin environment to use pyenv for managing python versions. I don't have admin rights so I run the setup with the --no-admin flag. There were some depend

Solution 1:

I found a solution for mapping pre-installed python binaries in pyenv (without using pyenv install <version>), however, it will only work for python versions installed using setup-x86_64.exe. Python is quite troublesome to compile in Cygwin.

  1. Install pyenv
git clone https://github.com/pyenv/pyenv.git ~/.pyenv
echo'export PYENV_ROOT="$HOME/.pyenv"' >> ~/.bashrc
echo'export PATH="$PYENV_ROOT/bin:$PATH"' >> ~/.bashrc

  1. Install Python using setup-x86_64.exe. For this example I installed the following packages:

    • python3 (version 3.6.9)
    • python36-pip
    • python36-virtualenv (optional, in case you work with virtualenv)

  2. To manually add an existing python version to pyenv, create a folder .pyenv/versions/<your-version-name>/bin and add link to binaries there:

mkdir ~/.pyenv/versions/3.6.9/bin/
cd ~/.pyenv/versions/3.6.9/bin/

ln -s /usr/bin/python3.6m.exe python3.6
ln -s python3.6 python3
ln -s python3 python

ln -s /usr/bin/pip3.6 pip3.6
ln -s pip3.6 pip3
ln -s pip3 pip

ln -s /usr/bin/virtualenv-3.6 virtualenv-3.6
ln -s virtualenv-3.6 virtualenv-3
ln -s virtualenv-3 virtualenv

PS: I imagine that other python versions can be installed through the regular windows system and symlinked likewise inside cygwin.

Solution 2:

Even though you have libffi-devel installed (which is needed in the first place), you won't be able to compile _ctypes and certain other extension modules due to a long-known bug in distutils for finding the import libraries needed to link extension modules with requirements on third-party libraries (such as libffi in this case).

There is a recently updated pull request to fix this issue, which has been sitting in wait of review for almost two years now. If you'd like to test the PR, and maybe add a comment to it confirming that it works and is needed, it might help move it along to getting merged...

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