JSON and XML — How Devices Talk Data

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Learning Objectives

  • Read and write basic JSON in Python
  • Parse a simple XML string
  • Know when you'll see each format in the real world

JSON: Lighter, Modern, Everywhere

Most modern REST APIs (including Cisco DNA Center) speak JSON -- lightweight, human-readable, maps directly onto Python dicts and lists. XML is older and heavier but still shows up in legacy systems and NETCONF.

import json

data = {
    "hostname": "router1",
    "interfaces": [
        {"name": "Gig0/0", "status": "up"},
        {"name": "Gig0/1", "status": "down"},
    ],
}

json_string = json.dumps(data, indent=2)
print(json_string)

parsed = json.loads(json_string)
print(parsed["interfaces"][0]["status"])

XML — Still Around in NETCONF

Same data, XML-style, parsed with the standard library.

import xml.etree.ElementTree as ET

xml_string = """<device>
  <hostname>router1</hostname>
  <interface name="Gig0/0">up</interface>
</device>"""

root = ET.fromstring(xml_string)
print(root.find("hostname").text)
print(root.find("interface").attrib["name"])

📝 Exercise: Convert and Filter Device Inventory

Given a JSON string of multiple devices, parse it, filter to only devices with status 'down', and print a clean report line for each one. Then do the same for the XML version below using ElementTree.

code.py
Output

            

        

    


    

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