python-pip : ImportError: cannot import name main

Question

I am using Debian 9.5 Stretch release. I am having import error while using pip. When I try using pip it says:

However I can use python:

I have two versions of python installed: 2.7 and 3.5

Output of which pip : /usr/bin/pip

When I tried reinstalling it using apt-get pip worked completely fine for the first time but the next time it shows the same error

Contents of /usr/bin/

Don't know whats the problem.

Answer 1

This most likely happened because you were using two different package managers (dpkg or its frontend apt-get, and pip itself) on the same prefix (/usr). I assume that either

• a recent apt-get upgrade updating some dependencies, but some other files that were installed by pip didn't get updated because dpkg and apt-get simply didn't know about them OR
• you removed a package with apt-get remove, and as apt-get wasn't aware of anything using this package (as the other package was installed by pip and thus not in the dpkg database), it didn't warn you about breaking other packages.

Without knowing which packages were installed with which package manager, I cannot give you any really specific advice how to repair your system, only general advice:

Don't use multiple different package managers. Only ever use one package manager for a given (sub-)tree of your filesystem, or you will get inconsistencies and/or conflicts. Debian's package manager for the /usr tree is called dpkg, and without calling it noone should ever touch /usr.

It certainly doesn't help that most python-related people you'll encounter try to push pip, even going as far as telling you to sudo pip install; don't. There are distro packages containing python stuff for a reason. Also see this related question on AskUbuntu and this answer on StackOverflow.

---

You can try to repair the mess by installing a fresh pip with

apt-get purge python-pip python3-pip
apt-get install python-pip python3-pip

however there may be files left behind that might interfere, which dpkg doesn't know about as they were installed by pip. The sure-fire way would be checking all files under /usr/lib/python* whether they belong to a debian package, and if not, delete them without exception.

Again, only use dpkg and its frontend tools like apt-get, aptitude, synaptic, ... to modify /usr. If you need to install anything system-wide that's not available as .deb package, either create a package and install it with dpkg, or install it under /usr/local.

Answer 2

Set python2.7 as default:

sudo update-alternatives --config python

select python2.7.

Remove pip:

sudo python -m pip uninstall pip
sudo apt purge --autoremove python-pip

Reinstall it:

sudo apt install python-pip

Check the pip --version:

pip 9.0.1 from /usr/lib/python2.7/dist-packages (python 2.7)

Do not upgrade pip to the latest version.