How to update an existing Conda environment with a .yml file

Prepping your command

Match the .yml and Conda environment names

Before launching into your update, check that your .yml file's name entry syncs with your intended update's Conda environment name. If there's no match, update the .yml or switch up the command:

# Naming the baby right to avoid identity crisis
conda env update --name myenv --file local.yml --prune
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This ensures you don’t call forth a new environment when all you wanted was an update.

Say 'bye-bye' to the active environment

To avoid clashes with running programs or loaded packages, it's best to deactivate your environment first:

# Let's give it a short nap so we can do some cleaning
conda deactivate 
conda env update --name myenv --file local.yml --prune
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Got stacked environments? No sweat!

For the next-level folks dealing with stackable environments, here's how you take care of them:

# When it comes to stacked environments, the base is your friend 
conda activate base
conda env update --name myenv --file local.yml --prune
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This approach stabilizes nested activation, smoothing out dependency management for your Conda environment.

Common pitfalls and how to dodge them

Encourage reactivation

The sheer joy of updating environments comes with a small to-do: reenter the environment.

# Wakey wakey! Time to see the new you!
conda deactivate
conda env update --file whatever.yml --prune
conda activate myenv
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Remember to use the correct environment name when reactivating. Or else, you may find yourself lost in Conda land.

When you update, think expansion, not replacement

The best updates build upon the existing environment, not completely overthrow it. So, review those .yml files carefully to ensure your invited guests won't evict the original housemates.

Nailing seamless updates

Anchor your versions

Developers, beware of version mismatch. Define version constraints in your .yml file, as unwanted major upgrades may cause a compatibility turmoil.

Resolve with care

Conda's solver loves to find the best possible matches for you. So, make sure your .yml file is chock-full of compatible and sufficient dependencies. The solver might face eviction without it!

Variables demand consistency

If your environment revolves around specific variables, make sure those are a part of your .yml update. Supplementing with conda env config vars set is a great move to maintain consistency.