Why are there multiple install commands on Anaconda Cloud?

Question

When searching a package in Anaconda Cloud, there are often multiple commands one could use to install a package. For example,

conda install -c conda-forge xxx 
conda install -c conda-forge/label/gcc7 xxx 
conda install -c conda-forge/label/cf201901 xxx

What's the difference between them?

Answer 1

Labels

Channel maintainers have an option to add labels to their package builds. Anaconda Cloud suggests using labels as a tool for organizing the development cycle. What the labels mean is totally up to the channel maintainer, so there's no general answer that will cover it all. When a label isn't provided, then default main is assigned.

Only advanced users should ever need to use a label. Most users should simply use the default specification:

conda install -c conda-forge xxx 

Example: gcc7

Let's look at a specific use case taken from your example. The gcc7 label is used by the Conda Forge channel maintainers to designate packages that have been compiled under a different toolchain than the packages they provide under their main tag. This gcc7 toolchain is designed to more closely match that which is used by the official channels (what you'd get from -c defaults) and thereby yield binaries that are compatible. You can read all about it in this issue on the Conda Forge repo.