Freezing PIP versions in a Docker container and creating requirements.txt

Tiempo de lectura: < 1 minuto

We will learn today how to freeze versions and update your container with a fixed requirements.txt.

docker exec -it nombre_contenedor /bin/bash

• This leaves you in the terminal inside the container.
• Make sure to be in the folder where you installed your packages or where your venv is located.

Generate requirements.txt

Inside the container, execute:

pip freeze > requirements.txt

• This generates a file named ‘requirements.txt’ with the exact versions of all installed libraries.
• You can copy it outside the container using:

docker cp nombre_contenedor:/app/requirements.txt ./requirements.txt

Change ‘/app/’ to the path inside the container where your project is located.

Instead of running a long list of ‘pip install’ commands, do something like:

COPY requirements.txt . RUN pip install --no-cache-dir -r requirements.txt

• This freezes versions automatically and makes the image more reproducible.

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Rebuild the container

docker-compose up -d --build

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With this you avoid errors like Pydantic v2 or bcrypt that appear “out of the blue” when rebuilding the image.