Learning Objectives

By the end of this article, you will:

• Understand the differences and similarities between PowerShell, PowerCLI, and Python.
• Learn basic scripting structures in PowerShell and Python.
• Execute your first script that combines Python and PowerCLI to automate a simple VMware task.

My Personal Repository on GitHub

VMware Repository on GitHub

Prerequisites

• Completed Article 1 (PowerCLI and Python are installed).
• Access to a VMware vSphere environment (lab or production).
• A Windows system (PowerCLI requires Windows PowerShell).

1. PowerShell, PowerCLI, and Python — How They Work Together

• PowerShell: A Windows command-line shell and scripting language.
• PowerCLI: A set of modules that plug into PowerShell, letting you control VMware vSphere, NSX, and Aria with simple commands.
• Python: A versatile scripting language, popular for orchestrating and extending automation.

You can run PowerCLI cmdlets directly in PowerShell, or orchestrate more complex logic by having Python scripts call PowerShell commands.

2. Basic Syntax: PowerShell vs Python

PowerShell Basics

• Cmdlets start with a verb-noun pattern (Get-VM, Start-VM).
• Variables use $.
• Comments start with #.

Example:

# List all VMs
Get-VM

# Store VM count in a variable
$vmCount = (Get-VM).Count
Write-Output "There are $vmCount virtual machines."

Python Basics

• Variables don’t use a special symbol.
• Comments start with #.
• Use print() for output.

Example:

# List of VM names
vm_list = ['Web01', 'App01', 'DB01']

# Print how many VMs
print(f"There are {len(vm_list)} virtual machines.")

3. Your First Automated Task: Calling PowerCLI from Python

The simplest way for Python to interact with PowerCLI is by executing PowerShell scripts from within a Python program.

Step 1: Create a PowerShell Script

Let’s start by writing a script that lists all VMs and saves them to a text file.

Save this as list_vms.ps1:

# Import PowerCLI
Import-Module VMware.PowerCLI

# Connect to vCenter (update with your details)
Connect-VIServer -Server <vcenter-address> -User <username> -Password <password>

# List VMs and output to file
Get-VM | Select-Object Name, PowerState | Out-File -FilePath C:Tempvm_list.txt

Replace <vcenter-address>, <username>, and <password> with your real values.

Step 2: Execute PowerShell Script from Python

Now, use Python to call that script. Here’s a basic example:

import subprocess

# Define the PowerShell script path
ps_script = r"C:Templist_vms.ps1"

# Run the PowerShell script
completed_process = subprocess.run([
    "powershell.exe",
    "-ExecutionPolicy", "Bypass",
    "-File", ps_script
], capture_output=True, text=True)

# Print the output (if any)
print("Script Output:", completed_process.stdout)
if completed_process.stderr:
    print("Errors:", completed_process.stderr)

4. Diagram: Workflow — Python Driving PowerCLI

Legend:

• Python orchestrates automation.
• PowerShell/PowerCLI connects to VMware and runs the actions.

5. Troubleshooting Tips

• Execution Policy Error: If you see a policy restriction, use: Set-ExecutionPolicy -ExecutionPolicy RemoteSigned -Scope CurrentUser
• Script Fails to Connect: Double-check credentials and vCenter server address.
• Output File Missing: Ensure C:Temp exists or update the output path.

6. Further Reading

• VMware PowerCLI Documentation
• Python subprocess docs
• PowerShell Official Docs

7. Conclusion and Next Steps

You’ve learned the basics of both PowerShell and Python, and you’ve seen how to use Python to execute a PowerCLI script. This opens up a world of automation possibilities, you can now combine VMware commands with Python’s data handling and logic.

In Article 3, you’ll connect to vCenter and retrieve detailed VM info using this combined approach.

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