Following my previous post, today I wanted to see if I could replace my pyenv and pyenv-virtualenv usage with uv.

Install uv

If you haven’t done it yet, you need to first install uv using either this method or one of the methods described in the documentation:

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brew update
brew install uv

Install Python

uv can detect Python versions installed in different ways in the system or it can install its own copies. You can check which ones are installed, using this command:

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uv python list --only-installed

Now we are going to install the latest (at the time of writing) version of Python:

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uv python install 3.13.1

Create a virtual environment

Creating virtual environment with uv is quite easy. We can do it in this way:

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uv venv --python 3.13.1 --prompt my-project

With --python 3.13.1 we specify the Python version we want and with --prompt my-project we customise the text that will appear in the prompt.

As the output will say, we can simply activate the environment with this command:

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source .venv/bin/activate

Automatically activate the virtual environment

Running source .venv/bin/activate every time we enter the project directory can be boring. We can automate this by using direnv.

direnv is a tool which can automatically set environment variables or run simple commands when we enter inside a directory.

You can install it with:

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brew install direnv

Once it’s installed, we need to add this configuration inside our .zshrc:

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eval "$(direnv hook zsh)"

or, in case we are using bash, we need to do it inside .bashrc:

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eval "$(direnv hook bash)"

At this point simply close and reopen your terminal (it’s the quickest way to reload the configuration) and finally create a file named .envrc inside your project folder, containing these two lines (or append these two lines in case you are already using this file):

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export VIRTUAL_ENV=$PWD/.venv
export PATH=$VIRTUAL_ENV/bin:$PATH

After you save this file and you get back to your terminal, you will get an error like this:

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direnv: error /Users/andrea/Projects/my-project/.envrc is blocked. Run `direnv allow` to approve its content

Just run that command to allow direnv to load your configuration:

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direnv allow

Installing Python packages

At this point you can use uv pip (which is a drop in replacement for pip with a few limitations) just like you would use pip:

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uv pip install requests

Make an alias for uv pip

If you are happy to use the uv version of pip, you can use it anywhere, even in virtual environments which are not managed by uv. You can create an alias by adding this to your .zshrc (or .bashrc etc…)

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alias pip="uv pip"

This way, every time you invoke pip, you will use the uv version:

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pip --version

Conclusion

Using uv pip, uv venv and uv python you can definitely speed up Python installation, virtual environments creations and Python packages installation.

But uv is much more. You can also manage dependencies, lock them and do many other things. At this point I don’t feel like switching completely to this tool, especially because a few things (like dependencies locking) are not standard across Python ecosystem and the risk is to use a workflow which is not supported by other existing tools (for example if you are using dependabot you won’t be able to just use uv.lock file, you will need to extract requirements.txt files)

My final advice is to use just the parts which are compatible with your existing workflow and wait until a standard for locking dependencies will be universally accepted, before jumping in with both feet.