How to avoid using conda-forge packages unless necessary?

Question

I'm running into a minor but annoying issue with conda when installing individual packages from conda-forge. Typically I'd run something like this:

conda install -c conda-forge somepackage

This has the effect of frequently updating other packages using conda-forge: almost always ca-certificates, certifi and openssl; and sometimes major packages like python, numpy etc (all from conda-forge). I suspect these updates are not strictly necessary; those packages get pulled in using some logic along the lines of "in order to install the latest version of somepackage I need python>=3.8 but the current python is 3.7; I can use conda-forge, so I'll get the latest python from conda-forge which is newer than the one in default".

What I would like to accomplish is: install any version of somepackage (not necessarily latest) while installing as little as possible from conda-forge. In particular, if there is a choice between keeping an already installed package and upgrading, I always want to keep; and if there is a choice between default channel and conda-forge, I always want default (even if those choices result in ending up with older versions of the new packages I'm trying to install, and/or their new dependencies - but not if they result in the install being impossible).

How do I accomplish this?

Answer 1

Generally, I endorse the conclusion in @jakub's answer: Define a reasonable global channel priority and try to avoid using ad hoc specifications via the --channel|-c argument.

There are some additional options that may be worth pointing out:

1. Specify that a particular package should come from a given channel with

    conda install conda-forge::somepackage
   

   and this will not change the channel priority.

2. Explicitly list channel priorities in the install command:

    conda install -c defaults -c conda-forge somepackage
   

   which puts defaults with top priority.

3. Define and manipulate environments through YAML files. YAMLs include a channels section, so you can be explicit about the priority. If you require a new package in the environment, it can be added to the YAML - let's say env.yaml - and that edit can be transferred to the environment with

    conda env update -f env.yaml