Installing Pip in Python 2 environments that don't provide it already
In theory any modern version of Python 2 (or Python 3) is bundled
pip, although it may be an out of date version that you could
update (with something like '
python2 -m pip install --user --upgrade
pip'). In practice, some Linux distributions split
pip off into
its own package and have stopped providing this separate package
for their version of Python 2. This is definitely the case for
Fedora 32, and may soon be the case for other distributions. If you
still want a Python 2 version of Pip (for example so that you can
keep updating the Python 2 version of the Python language server), you need to install one by hand, somehow.
When I had to do this on my Fedora 32 machine I was lucky enough
that I had already done an update of the Python 2 pip on one machine
where I used '
--user' to install the new version in my $HOME, so
I had all of the Pip code in .local/lib/python2.7/site-packages and
could just copy it over, along with .local/bin/pip2. It turns out
that this simple brute force approach is probably not necessary
and there is a completely convenient alternative, which is different
than the situation I expected before I started writing this entry.
(Since pip is normally installed with your Python, I expected that bootstrapping pip outside of that was not very well supported because it was infrequently used. For whatever reason, this is not at all the case currently.)
The pip people have an entire document on installing pip that walks you through a number of options. The important one for my case is Installing with get-pip.py, where you download a get-pip.py Python program to bootstrap pip. One of the options it supports is installing pip as a user package, resulting in a .local/bin/pip2 for you to use. The simple command line required is:
python2 get-pip.py --user
One of the reasons this works so well is that, well, get-pip is
actually pip itself (the full version, as far as I know). The comment
at the start of
get-pip.py explains what is going on so well that
I am just going to quote it wholesale:
You may be wondering what this giant blob of binary data here is, you might even be worried that we're up to something nefarious (good for you for being paranoid!). This is a base85 encoding of a zip file, this zip file contains an entire copy of pip (version 20.2.4).
Pip is a thing that installs packages, pip itself is a package that someone might want to install, especially if they're looking to run this get-pip.py script. Pip has a lot of code to deal with the security of installing packages, various edge cases on various platforms, and other such sort of "tribal knowledge" that has been encoded in its code base. Because of this we basically include an entire copy of pip inside this blob. We do this because the alternatives are attempt to implement a "minipip" that probably doesn't do things correctly and has weird edge cases, or compress pip itself down into a single file.
As a sysadmin, I fully support this very straightforward and functional approach to bootstrapping pip. The get-pip.py file that results is large for a Python program, but as installers (and executables) go, 1.9 Mbytes is not all that much.
However, there is a wrinkle probably coming up in the near future. Very soon, versions of pip itself will stop supporting Python 2; the official statement (currently here) is:
pip 20.3 was the last version of pip that supported Python 2. [...]
(The current version of pip is 20.3.3.)
The expected release date of pip 21.0 is some time this month. At some time after that point, get-pip.py may stop supporting Python 2 and you (I) will have a more difficult time bootstrapping the Python 2 version of pip on any machine I still need to add it on. Of course, at some point I will also stop having any use for a Python 2 pip, because the Python language server itself will drop support for Python 2 and I won't have any reason to upgrade my Python 2 version of it.
(Pip version 21.0 should fix, or at least work around, a long stall on startup that's experienced in some Linux configurations.)
PS: What PyPy will do about this is a good question, since they are so far planning to support Python 2 for a very long time. Perhaps they will freeze and ship pip 20.3.3 basically forever.