Source: 📖 Effective Python item 83

Recreating dependencies with freeze

If you need to transfer a project elsewhere, such as a server in a database or another workstation, all dependencies will need to be available on the destination system in order to successfully use the project—all required packages need to be installed. This is made easy with the pip freeze command, which will write all dependencies to a file which is called requirements.txt by convention.

(myproject) $ python3 -m pip freeze > requirements.txt
(myproject) $ cat requirements.txt
numpy==1.16.2
requests==2.21.0
urllib3==1.24.1

This file can then be used in another virtual environment to install all required dependencies by using -m pip install -r on the requirements.txt file inside the new virtual environment.

(otherproject) $ python3 -m pip install -r requirements.txt
(otherproject) $ python3 -m pip list
numpy==1.16.2
requests==2.21.0
urllib3==1.24.1

See also:

• Do not install packages globally
• Using venv to create a virtual environment