Python Service

Python Script

This guide demonstrates the basic concepts around creating and executing a Python script service within IAG5.

Prerequisites

• You will need a Git repository setup with a Python script within it.

• Review the Create Repository command to understand how to create a repository.

Create Python Script

The command iagctl create python-script will create the Python script service.

The command shown below creates a Python script service within IAG5 called simple-python that will leverage a previously configured repository called gateway-resources.

>_ iagctl create python-script simple-python --repository gateway-resources --working-dir pythonscripts --filename main.py

Python Scripts Directory

Important information to understand the structure of gateway-resources is presented below.

├── README.md
├── ansibleplaybooks
├── pythonscripts
│   ├── main.py
│   └── requirements.txt
└── opentofuplans

Notice that the Python script exists in a directory called pythonscripts. This is denoted using the --working-dir flag.

Inside the pythonscripts directory there is an actual script called main.py. This is denoted with the --filename flag.

If the Python script requires external libraries, place a requirements.txt file within the working directory. IAG5 will automatically manage the dependencies.

Verify Python Script Service

Details about the previously created Python script service can be viewed by running the describe command.

>_ iagctl describe python-script simple-python

Output:

Name:        simple-python
Repo Name:   gateway-resources
Working Dir: pythonscripts
FileName:    main.py
Decorator:   
Description: 
Tags:

Execute Python Script

Executing a Python script is simple from IAG5 by utilizing the run python-script command.

Review the contents of main.py in the Python script shown below.

# main.py
from netmiko import ConnectHandler
import argparse

def main():
    parser = argparse.ArgumentParser(description="Netmiko Command Service")
    parser.add_argument('--command', required=True, help="Command to run")
    parser.add_argument('--host', required=True, help="Host to connect to")
    args = parser.parse_args()
    # YOUR EXECUTION CODE GOES BELOW THIS LINE    

    cisco1 = {
        "device_type": "cisco_ios",
        "host": args.host
    }
    with ConnectHandler(**cisco1) as net_connect:
        output = net_connect.send_command(args.command)
    
    print(output)

if __name__ == "__main__":
    main()

This script requires the netmiko library. This is specified in the requirements.txt file located in the working-dir when creating the service.

netmiko==4.3.0

When executing a Python script using the run python-script command, IAG5 will automatically look for the requirements.txt file in the working directory that was specified during the creation of the service.

IAG5 will then create the virtual environment with all the dependencies specified in requirements.txt and execute the script within that virtual environment. This feature allows for easy management of Python dependencies.

The Python script takes in two inputs: command and host. They can be specified using the --set flag.

>_ iagctl run python-script simple-python --set host=10.0.0.1 --set command="show version"

Output:

Start Time:   2024-01-01T12:00:00Z
End Time:     2024-01-01T12:00:01Z
Elapsed Time: 1.372672s
Return Code: 0
================================================================================
                           System Version Information
================================================================================

...truncated for document

Stderr:

IAG5 will take the key=valuesdefined via --set command and then pass it to the Python service.

For this example, the following command is run by IAG5 on the backend:

<python-executable> main.py --host=10.0.0.1 --command="show version"

Barebones Script With Inputs

The most important part of working with a Python script is how to get the arguments into the script. A key integration between IAG5 and a Python service is the ability to read key=value from the command line.

Every Python script that is written will have something that looks like the Python code below. You can follow the barebones example to get started with accepting input arguments.

# main.py
import argparse


def main():
    parser = argparse.ArgumentParser(description="iagctl example")
    parser.add_argument('--name', required=True, help="Name to greet")
    args = parser.parse_args()
    name = args.name
    # YOUR EXECUTION CODE GOES BELOW THIS LINE    

    print(f"Hello, {name}")

if __name__ == "__main__":
    main()

Managing Python Services

For reference and understanding, below is a flow outline depicting the steps IAG5 moves through as it manages the dependencies for a Python based service.

1. Start Python Service →
2. Does requirements.txt exist?
3. If Yes, get contents of requirements.txt. Go to step 4.
4. Does virtual environment ("venv") exist with the contents?
   1. If Yes, go to step 5.
   2. If No, complete these steps:
      1. Find a Python interpreter.
      2. Create virtual environment.
      3. Install requirements.
5. Use existing venv. Go to step 6.
6. Run Python Script with venv.

Decorators

It is possible to put restrictions around the inputs that are accepted by a Python script by utilizing decorators. For more information on decorators, please refer to this guide.

CLI Reference

For command references see → Command References Index

• iagctl create service python-script

• iagctl run python-script

• iagctl get services

• iagctl describe service

• iagctl delete service