How to create a lock file from installed packages (or from requirements.txt file)

[czechnology]

Question

When I'm creating a lock file with uv lock, it will always lock the newest available versions. Is it possible to create a lock file which matches the versions installed in the venv? I have not been able to find a combination of options which would achieve this.
Alternatively, can I create a lock file from requirements.txt file?

I would need this for the process of migrating to uv: I would like to keep the pinned versions the same as before to keep the change minimal.

Platform

No response

Version

No response

[czechnology]

In practice, for the first option I would install the packages based on the requirements.txt file and then lock.

rm -rf .venv
uv venv
uv pip install -r requirements.txt
uv lock --something?

[konstin]

You can use uv pip freeze to record the installed versions and use them as constraint dependencies for the first locking (you might need some manual editing for the transition from one environment to universal locking)

[czechnology]

That is not what I'm going for - I already have the dependencies I want to keep available as requirements.txt files. I am trying to figure out how to make a uv.lock file with the same versions as those in the requirements files. One way I thought would be doable is to first install those versions into a virtualenv and then somehow create a uv.lock file which would reflect the installed versions instead of the newest ones available.

[charliermarsh]

You can pass the requirements.txt as a constraint:

echo "anyio" > requirements.in
uv pip compile requirements.in -o requirements.txt
uv add -r requirements.in -c requirements.txt

[czechnology]

Thanks, @charliermarsh, that is an interesting approach but gets me forward, thanks!

# Create a backup of pyproject.toml
cp pyproject.toml pyproject.backup

# Set the pinned requirements to be the constraints in pyproject.toml
uv add -r requirements.txt -c requirements.txt

# uv.lock is now created

# Now that we have a lock file, let's revert the original config file
mv pyproject.backup pyproject.toml

[zanieb]

This is also covered in #12382, to an extent.

[czechnology]

That will be a useful part of the docs, @zanieb, thanks!