I should keep track of what Python packages I install through pip
These days I'm increasingly making use of installing Python packages
through pip, whether this is into a PyPy environment or with 'pip install --user' for things
like python-lsp-server. Having done this for a
while, complete with trying to keep up with potential package
upgrades, I've come to the conclusion that I should explicitly keep
track of what packages I install, recording this in some place I
can find it again.
There are two problems (or issues) that push me to this. The first
is that as far as I know, Pip doesn't keep track of a distinction
between packages that you've asked it to install and the dependencies
of those packages. All of the packages show up in 'pip list', and
any can show up in 'pip list --outdated'. My understanding is
that in the normal, expected use of Pip you'll keep track of this
in your project in a requirements file,
then use that to build the project's virtualenv. This is not really
the model of installing commands, especially commands like
python-lsp-server
that have install time options.
The second issue is that Pip installed packages are implicitly
for a specific version of Python. If you
rely on the system Python (instead of your own version) and that
version gets upgraded, suddenly 'pip list' will report nothing
(and you will in fact have no packages available). At this point
you need to somehow recover the list of installed packages and
re-install all of them (unless you resort to unclean hacks).
Explicitly keeping track of this list in advance is easier than
having to dig it out at the time.
Having an explicit list helps in other situations. Perhaps you started out installing all of your tools under CPython, but now you want to see how well they'll work under PyPy. Perhaps you're building a new PyPy based environment with a new version of PyPy and want to start over from scratch. Perhaps you think package versions and dependencies have gotten snarled and you're carrying surplus packages, so you want to delete everything and start over from scratch.
(Starting over from scratch can also be the easiest way to get the
best version of dependencies, since the packages you're directly
installing may have maximum version constraints that will trip you
up if you just directly 'pip install --upgrade ...' dependencies.)
PS: Possibly there's ways to do all of this with Pip today, especially things like 'upgrade this and all of its dependencies to the most recent versions that are acceptable'. I'm not well versed in Pip, since mostly I use it as a program installer.
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