[Day#2 PyATS Series] Setting up Python Virtual Environments for pyATS for Cisco [Python for Network Engineer]

1. Introduction on the Key Points

In the evolving world of network automation, learning how to integrate Python for Network Engineer tasks has become essential. If you’re a Cisco network professional looking to automate testing, validation, or configuration, pyATS (Python Automated Test System) is your best friend.

In this second article of our multi-day pyATS series, we will walk through setting up a clean and isolated Python virtual environment. This setup allows you to manage dependencies, keep your automation scripts clean, and prepare for real-world projects involving Cisco routers, switches, firewalls, and SD-WAN platforms.

By the end of this article, you will:

• Understand why virtual environments are crucial
• Set up a venv for pyATS using best practices
• Install pyATS core components and verify their versions
• Begin your journey toward automating network testing the right way

2. Topology Overview

Though today’s task is environment setup, here is the logical flow we’ll be using in later labs:

All devices will be accessed via SSH from your local machine using the testbed YAML file (which we’ll preview later).

3. Topology & Communications

We’ll focus on:

• pyATS virtual environment setup
• Installing required modules (pyats, unicon, genie)
• Validating connectivity to testbed (router/switch)

This is the foundation for running real-world tests like interface status checks, configuration drift detection, or ping reachability.

4. Workflow Script

Here’s a simplified script that validates your pyATS environment is set up correctly:

# Step 1: Create Python venv
python3 -m venv pyats_lab_env

# Step 2: Activate it
source pyats_lab_env/bin/activate  # For Linux/macOS
# pyats_lab_env\Scripts\activate   # For Windows

# Step 3: Install pyATS
pip install pyats[full]

# Step 4: Confirm installation
pyats version check

# Optional: Upgrade pip
python -m pip install --upgrade pip

5. Explanation by Line

• python3 -m venv pyats_lab_env: Creates a self-contained environment called pyats_lab_env
• source pyats_lab_env/bin/activate: Activates the environment so that all installations remain isolated
• pip install pyats[full]: Installs the entire pyATS suite, including unicon and genie libraries
• pyats version check: Validates that pyATS and its components are correctly installed

6. testbed.yml Example

testbed:
  name: cisco_testbed
  credentials:
    default:
      username: admin
      password: cisco123

devices:
  R1:
    os: iosxe
    type: router
    connections:
      cli:
        protocol: ssh
        ip: 192.168.1.1

Save this as testbed.yml in your project folder.

7. Post-validation CLI Screenshots (Real expected output)

After installation, run:

pyats version check

Expected output:

| Package      | Version  |
|--------------|----------|
| pyats        | 23.5     |
| unicon       | 23.5     |
| genie        | 23.5     |

FAQs

Q1: Why should I use a Python virtual environment when working with pyATS?

Answer:
A Python virtual environment isolates your pyATS installation and its dependencies from the system-wide Python setup. This is crucial because:

• It prevents conflicts between different Python packages or versions.
• Allows you to create multiple environments for different projects (e.g., pyATS for Cisco, Ansible automation).
• Keeps your base operating system clean and stable.
• Makes it easier to upgrade or remove pyATS without affecting other Python applications.

Q2: What Python version should I use for setting up pyATS?

Answer:
Cisco officially supports Python 3.6 to 3.10 for pyATS. It is recommended to use:

• Python 3.8 or 3.9 for maximum compatibility.
• Avoid using Python 3.11+ as some libraries might not yet fully support it.
• You can check your Python version with:

python3 --version

Q3: How do I create a Python virtual environment for pyATS?

Answer:
Follow these steps:

1. Install Python and venv if not already installed: sudo apt update sudo apt install python3 python3-venv
2. Create a virtual environment: python3 -m venv pyats_venv
3. Activate the environment: source pyats_venv/bin/activate
4. Install pyATS: pip install pyats[full]

Q4: How do I know my virtual environment is active?

Answer:
When a virtual environment is active:

• Your terminal prompt changes to show the environment name (e.g., (pyats_venv) user@server).
• which python or which pip points to the virtual environment’s directory instead of the system path.
• Any packages installed via pip go into the isolated environment folder.

Q5: Can I deactivate or remove a virtual environment without affecting pyATS?

Answer:
Yes. To deactivate:

deactivate

To remove the environment completely:

rm -rf pyats_venv

This will not harm your system Python or other projects since everything is contained within the pyats_venv directory.

Q6: How can I manage multiple virtual environments for different projects?

Answer:
You can create multiple environments, each with different package versions:

python3 -m venv pyats_project1
python3 -m venv pyats_project2

Activate the one you need before running your scripts. Tools like virtualenvwrapper or pyenv can help manage multiple environments easily.

Q7: What is the difference between venv and virtualenv for pyATS?

Answer:

• venv: Built-in with Python 3.x, simpler to use, no extra installation needed.
• virtualenv: A third-party tool that works for both Python 2 and 3 and offers additional features like faster environment creation.
  For most pyATS use cases, venv is sufficient and recommended.

Q8: Do I need to activate the virtual environment every time I use pyATS?

Answer:
Yes. Each time you open a new terminal session and want to work with pyATS, you must activate the environment:

source pyats_venv/bin/activate

This ensures you’re using the correct Python interpreter and installed packages.

YouTube Link

Watch the Complete Python for Network Engineer: Setting up Python Virtual Environments for pyATS (Ping Tests) using pyATS (Vendor-Agnostic) – Cisco, Arista, Palo Alto, Fortigate Lab Demo & Explanation on our channel:

Join Our Training

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• Turn you into a confident Python for Network Engineer
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