Python Fundamentals for Network Automation

0s15★ 115 XP

Lesson 139Interactive lesson

Python Fundamentals for Network Automation

A structured lesson workspace with readable content, hands-on examples, and a clean path to completion.

Lesson format19 sections4 code blocks1 practice itemUpdated Oct 2, 2026

python

python3 -c "from netmiko import ConnectHandler; print('Netmiko ready')"

Python is the network automation language. Not because it's the only option — Go, Ruby, and shell scripts all work — but because the ecosystem of network libraries (Netmiko, NAPALM, Nornir, pyATS) is deepest in Python. If you're going to learn one language for network automation, this is it.

#The Basic Pattern#link

python

from netmiko import ConnectHandler

# Define the device
device = {
    'device_type': 'cisco_ios',
    'host': '10.10.20.10',
    'username': 'admin',
    'password': 'MyPassword',
    'secret': 'MyEnablePassword',
}

# Connect and run a command
with ConnectHandler(**device) as net_connect:
    net_connect.enable()
    output = net_connect.send_command('show ip interface brief')
    print(output)

    # Make a config change
    config_commands = [
        'interface GigabitEthernet0/5',
        'description Automation-added',
        'switchport mode access',
        'switchport access vlan 30',
    ]
    result = net_connect.send_config_set(config_commands)
    print(result)

    # Save
    net_connect.save_config()

That's the entire pattern. Connect to a device, run show commands, push config commands, save. Netmiko handles SSH, enable mode, prompt detection, and pagination. Whatever device type — `cisco_ios`, `cisco_nxos`, `juniper_junos`, `arista_eos` — the pattern is the same.

callout

The `with` statement matters. It ensures the connection is closed cleanly even if an exception occurs. Without it, a failure mid-script leaves stale SSH sessions on the device. Always use `with ConnectHandler(...) as net_connect` — it's the standard idiom.

#Parsing Output#link

python

import re

output = net_connect.send_command('show ip interface brief')

# Parse with regex
lines = output.split('\n')
for line in lines:
    match = re.match(r'(\S+)\s+(\S+)\s+\S+\s+\S+\s+(up|down|administratively down)\s+(up|down)', line)
    if match:
        interface, ip, status, protocol = match.groups()
        print(f'{interface}: {ip} — {status}/{protocol}')

Regular expressions are how you extract structured data from unstructured CLI output. The pattern `(\S+)` captures non-whitespace tokens; `\s+` matches one or more whitespace. That said — for modern devices and controllers, prefer JSON/XML output when available. Regex against CLI output breaks when the format changes; JSON doesn't.

#Looping Over Many Devices#link

python

from netmiko import ConnectHandler
import json

# Load device inventory from a JSON file
with open('devices.json') as f:
    devices = json.load(f)

# Run a command against every device
for dev in devices:
    print(f'=== {dev["host"]} ===')
    try:
        with ConnectHandler(**dev) as conn:
            conn.enable()
            version = conn.send_command('show version | include Version')
            print(version)
    except Exception as e:
        print(f'Error on {dev["host"]}: {e}')

# Expected devices.json:
# [
#   {"device_type": "cisco_ios", "host": "10.10.20.10", "username": "admin", "password": "x"},
#   {"device_type": "cisco_ios", "host": "10.10.20.11", "username": "admin", "password": "x"}
# ]

The pattern is: load inventory, loop over devices, wrap each connection in try/except so one failure doesn't stop the script. This scales from 2 devices to 2,000 with the same code. If you need parallelism (faster execution across thousands of devices), use Nornir or concurrent.futures — but the sequential pattern is the starting point.

#Code Exercise — Config Generator#link

★ 100 XPmedium

#The Complete Workflow#link

#Check Your Understanding#link

★ 15 XPeasy

exercise BLOCK (★ 15 XP)

Which Python library is most commonly used for SSH-based network device automation?

Select your proof vectors above

callout

Section 18 complete. You've covered automation concepts, controller-based networking, REST APIs, JSON, HTTP methods, DNA Center, CI/CD workflows, and Python fundamentals with Netmiko. This is the toolkit for modern network operations. Sections 19-21 cover network operations, configuration labs, and exam prep — coming in the final batch.

Lesson completion

Ready to resolve this lesson?

Finish the lesson once you have worked through the material. This awards ★ 115 XP.

Previous lesson

Lesson tools

Workspace

0% read

Lab notes

Notes persist per lesson.

The Basic Pattern Parsing Output Looping Over Many Devices Code Exercise — Config Generator The Complete Workflow Check Your Understanding

Content

Last updated

October 2, 2026

Agent Setup

Access lesson content programmatically for AI agents, LLMs, and automated pipelines.

Fetch as Markdown (Accept header)

curl -H "Accept: text/markdown" "https://vulnarex.com/api/content/lessons?courseSlug=complete-ccna-200-301&lessonSlug=8-python-fundamentals-network-automation&lang=en&format=markdown"

MCP Server Config (mcp.json)

{
  "mcpServers": {
    "vulnarex": {
      "command": "npx",
      "args": ["-y", "@modelcontextprotocol/server-fetch"],
      "env": { "MCP_FETCH_URL": "https://vulnarex.com" }
    }
  }
}

MCP Server Card/.well-known/mcp.json A2A Agent Card/.well-known/agent-card.json API Catalog/.well-known/api-catalog robots.txt/robots.txt

Laboratory sanity code

Isolate active probes on matched virtual networks and keep execution streams sandboxed.

from netmiko import ConnectHandler

# Define the device

device = {

'device_type': 'cisco_ios',

'host': '10.10.20.10',

'username': 'admin',

'password': 'MyPassword',

'secret': 'MyEnablePassword',

}

# Connect and run a command

with ConnectHandler(**device) as net_connect:

net_connect.enable()

output = net_connect.send_command('show ip interface brief')

print(output)

# Make a config change

config_commands = [

'interface GigabitEthernet0/5',

'description Automation-added',

'switchport mode access',

'switchport access vlan 30',

]

result = net_connect.send_config_set(config_commands)

print(result)

# Save

net_connect.save_config()

import re

output = net_connect.send_command('show ip interface brief')

# Parse with regex

lines = output.split('\n')

for line in lines:

match = re.match(r'(\S+)\s+(\S+)\s+\S+\s+\S+\s+(up|down|administratively down)\s+(up|down)', line)

if match:

interface, ip, status, protocol = match.groups()

print(f'{interface}: {ip} — {status}/{protocol}')

from netmiko import ConnectHandler

import json

# Load device inventory from a JSON file

with open('devices.json') as f:

devices = json.load(f)

# Run a command against every device

for dev in devices:

print(f'=== {dev["host"]} ===')

try:

with ConnectHandler(**dev) as conn:

conn.enable()

version = conn.send_command('show version | include Version')

print(version)

except Exception as e:

print(f'Error on {dev["host"]}: {e}')

# Expected devices.json:

# [

# {"device_type": "cisco_ios", "host": "10.10.20.10", "username": "admin", "password": "x"},

# {"device_type": "cisco_ios", "host": "10.10.20.11", "username": "admin", "password": "x"}

# ]

Python Fundamentals for Network Automation

#The Basic Pattern#link

#Parsing Output#link

#Looping Over Many Devices#link

#Code Exercise — Config Generator#link

#The Complete Workflow#link

#Check Your Understanding#link

Which Python library is most commonly used for SSH-based network device automation?

Ready to resolve this lesson?

Python Fundamentals for Network Automation

#The Basic Pattern#link

#Parsing Output#link

#Looping Over Many Devices#link

#Code Exercise — Config Generator#link

Generate a VLAN config block from data

#The Complete Workflow#link

#Check Your Understanding#link

Which Python library is most commonly used for SSH-based network device automation?

Ready to resolve this lesson?

Generate a VLAN config block from data