Auto‑Clean Python Dependencies with pipreqs and Pre‑Commit

After working on a Python project for a while, your .venv often accumulates libraries you no longer use, inflating the environment and slowing down builds. Your requirements.txt may be filled with unnecessary packages.

Increases environment size

Slows deployment and CI/CD pipelines

Causes version conflicts

Introduces unnecessary security vulnerabilities

In the example, three libraries— pandas, polars and requests —are installed, but only requests is actually needed.

Your code's actual dependencies

pipreqs

scans your source code and generates a new requirements.txt that contains only the packages you really import.

Installation is simple: pip install pipreqs Then run: pipreqs . --force This command overwrites the existing requirements.txt with a clean version.

Example of the original requirements.txt versus the cleaned one:

Requests==2.32.5
certifi==2025.10.5
charset-normalizer==3.4.4
idna==3.11
numpy==2.3.4
pandas==2.3.3
polars==1.34.0
polars-runtime-32==1.34.0
python-dateutil==2.9.0.post0
pytz==2025.2
requests==2.32.5
six==1.17.0
tzdata==2025.2
urllib3==2.5.0

Now you can recreate a clean virtual environment and install only the needed packages:

python -m venv venv
source venv/bin/activate   # on Windows: venv\Scripts\activate

pip install -r requirements.txt

Before committing, ensure the requirements.txt is clean.

Use Pre‑Commit for dependency cleanup

Automate the cleanup with a Git pre‑commit hook that runs pipreqs before each commit.

Set up Pre‑Commit

First install the tool: pip install pre-commit Initialize the hook in your repository: pre-commit install Create a .pre-commit-config.yaml file with the following content:

repos:
- repo: local
  hooks:
  - id: clean-python-deps
    name: Clean Python Dependencies
    entry: bash -c "pip install pipreqs && pipreqs . --force"
    language: system
    pass_filenames: false
    stages: [commit]

Test the hook:

git add .
git commit -m "test cleanup hook"

You will see output similar to:

(venv) PS C:\test> git commit -m "test cleanup hook"
Clean Python Dependencies................................................

With this setup, your dependency list self‑repairs on every commit.