Why should a tool like pyATS be installed in a Python virtual environment (venv)?

A venv is an isolated copy of the Python environment in its own folder, so packages installed there can be added, upgraded or removed without permanently changing the host system.

Installing packages system-wide has two problems. It can overwrite library versions that the OS or other tools depend on, and different projects often need different versions of the same library.

A virtual environment solves both:

• it is copied from the base environment but stays separate from it,
• it lives in an ordinary folder in the file system,
• once activated, pip install writes only into that folder,
• components can be updated or changed freely without the changes showing up in the host's configuration,
• if it breaks, you delete the folder and start again.

Creating one is built into Python 3:

python3 -m venv pyats-env
source pyats-env/bin/activate
pip install pyats[full]
pyats --help        # check the install

Installing also requires pip (Python's package manager) and git, which is used to clone example repos such as Cisco DevNet's pyats-sample-scripts.

Go deeper:

• Python tutorial — Virtual Environments and Packages — create, activate and install into a venv step by step.