Python Basics

In the previous lesson, you used EEM to automate tasks directly on a router.
EEM is powerful, but the applet runs inside a single device.

When you need to manage a fleet of devices from a central place, you write external scripts using Python.

Your Python script does not type CLI commands like a human. It sends structured requests to an API on the device, and the device replies with structured data in JSON.

Figure 1 – The four pieces behind every script that talks to a router

The Four Architecture Pieces

Four pieces work together every time a script talks to a router:

• The script you write: variables, lists, dictionaries, and loops that hold your logic.

• The library you import: the Python package doing the heavy lifting, such as requests or ncclient.

• The protocol on the wire: RESTCONF or NETCONF travelling between your script and the device.

• The device that answers: the Cisco IOS-XE router receiving the request, applying it, and replying.

This lesson covers the first piece: the plain Python logic you write to handle network data structures.

Every exam exhibit you read is built from these same building blocks. Master them to read any script instantly.

hostname = "R1"
ip_address = "192.168.1.1"
port = 830
enabled = True

Three types cover almost every networking value you will see:

• string: text in quotes, like "R1"

• integer: a whole number, like 830

• boolean: True or False (capitalized in Python)

Lists and Dictionaries

A list stores multiple values in order using square brackets:

interfaces = ["Gi0/0", "Gi0/1", "Gi0/2", "Gi0/3"]

print(interfaces[0])    # first element
print(interfaces[-1])   # last element

Output: