Because each virtual environment is separate from the main Python installation, each environment must have the required modules installed. While this can seem like a pain, pip makes it quite easy. After setting up the first virtual environment, a pip command called freeze allows you to generate a file called requirements.txt. This file can be copied into a new virtual environment and using pip install, all of the listed modules will be added from PyPI.

To generate a requirements.txt file in the current folder, use this command:

(cartoenv) C:PacktChapters>pip freeze > requirements.txt

After the file has been copied into a new virtual environment folder, activate the environment and pass the following command to read from the file:

(newenv) C:PacktChapters>pip install -r requirements.txt