If you’re working on a Python application, you’re probably using pip, and thus will need a
requirements.txt file along the way to handle your project dependencies (when deploying your application for example).
The most common way to generate a
requirements.txt file is to simply output the
pip freeze command in the file.
pip freeze > requirements.txt
This will list not only the packages you manually installed (top-level dependencies), but also all of their dependencies (low-level dependencies).
amqp==2.1.1 anyjson==0.3.3 beautifulsoup4==4.5.1 billiard==18.104.22.168 celery==4.0.0 Django==1.10.2 django-unixdatetimefield==0.1.4 djangorestframework==3.5.1 djangorestframework-bulk==0.2.1 kombu==4.0.0 pytz==2016.7 redis==2.10.5 requests==2.11.1 vine==1.1.3 wheel==0.24.0 gunicorn==19.6.0
While it is considered best practice to use this complete list of all dependencies, it can be a handful when trying to globally update your application packages, especially if you’re not familiar with the codebase and don’t know if a dependency is top-level or not. This can result in a headache of package compatibility issues.
A solution to that problem is to work with a second requirements file, where we’ll keep track of our application top-level dependencies:
Django==1.11.3 djangorestframework==3.5.1 celery beautifulsoup4==4.5.1 redis==2.10.5 requests django-debug-toolbar==1.6 djangorestframework-bulk
In this file, you’ll list your top-level dependencies, with or without a specific version.
# Installing the top-level dependencies, upgrading them if necessary pip install –r requirements-top-level.txt --upgrade # Updating requirements.txt pip freeze –r requirements-top-level.txt > requirements.txt
requirements.txt will contains the output of
pip freeze after the top-level dependencies have been installed, with the top-level and low-level dependencies nicely separated.
Django==1.11.3 djangorestframework==3.5.1 celery==4.0.0 beautifulsoup4==4.5.1 redis==2.10.5 requests==2.11.1 django-debug-toolbar==1.6 djangorestframework-bulk==0.2.1 ## The following requirements were added by pip freeze: amqp==2.2.1 anyjson==0.3.3 billiard==22.214.171.124 django-unixdatetimefield==0.1.4 kombu==4.1.0 pytz==2017.2 sqlparse==0.2.3 vine==1.1.4 wheel==0.29.0
For a fresh install, you can safely use
pip install -r requirements.txt