pip3 install not working - No module named 'pip._vendor.pkg_resources'

This solved it for me:

curl -sS https://bootstrap.pypa.io/get-pip.py | sudo python3

try use virtualenv for every specific project not messing with ubuntu subsystem.

Thanks @s_s.411

I solve this problem with the following commands:

curl -sS https://bootstrap.pypa.io/get-pip.py | sudo python3type pip3hash -rpip3

I ran into the same problem, on Ubuntu 16.04, using the system python 3.5.2 like you, with pip installed via apt (sudo apt install python3-pip) like you, having installed some packages in my home directory with pip3 install --user like you (documented in your chat with hoefling).

The solution was as follows:

1. Temporarily move away all packages installed with pip3 install --user:

mv ~/.local/lib/python3.5/site-packages{,_backup}

This made pip3 work again, but of course I wanted to keep the packages. (Note: just moving out setuptools was not enough; I am not sure which constellation of packages caused this.)

2. Install an upgraded pip into home directory:

pip3 install --upgrade --user pip

Now the pip3 command fails (ImportError: cannot import name 'main') because it's still called from the old /usr/bin/pip3 location in the current shell, as indicated by type pip3. To solve this, run:

hash -r

Alternatively, you can always fall back to typing python3 -m pip instead of pip3.

3. Restore the packages:

mv ~/.local/lib/python3.5/site-packages{_backup/*,}rmdir ~/.local/lib/python3.5/site-packages_backup

4. Now pip was working, but python3 -m 'import setuptools' failed with the same exception you saw, AttributeError: '_NamespacePath' object has no attribute 'sort'. This could be solved by uninstalling, then reinstalling the setuptools package in my home directory (uninstalling alone was not enough):

pip3 uninstall setuptoolspip3 install --user --upgrade setuptools

Finally, pip3 and the python3 -c 'import setuptools' are fine.