Reading Python Scripts

You can read Python data structures and you know the HTTP rules.
Now you put them together against the kind of code you will see in an exam exhibit.

Remember three RESTCONF principles:

• HTTPS on TCP port 443

• JSON format for data input and output

• A long URL pointing to a specific configuration item on the router

Figure 1 – Lab topology

PC1 runs Python with the requests library installed.
It reaches Cisco IOS-XE router R1 (192.168.1.1) over TCP port 443 to send RESTCONF traffic.

Script 1 — Simple GET Request

Here is the smallest networking script you can write.
It asks R1 for its GigabitEthernet0/1 configuration over RESTCONF:

import requests
import urllib3
urllib3.disable_warnings()

url = "https://192.168.1.1/restconf/data/Cisco-IOS-XE-native:native/interface/GigabitEthernet=0%2F1"
headers = {"Accept": "application/yang-data+json"}

response = requests.get(url, headers=headers,
                        auth=("admin", "cisco123"),
                        verify=False)

print(response.status_code)
print(response.json())

Walk through it line by line:

• import requests: Loads the HTTP library.

• urllib3.disable_warnings() and verify=False: Suppress SSL certificate warnings (acceptable in a lab, not in production).

• url: Points at one specific item on the router (GigabitEthernet0/1).

• headers: Tells R1 you want JSON, not XML.

• requests.get(...): Sends an HTTPS GET request with your credentials.

• auth=("admin", "cisco123"): Passes HTTP Basic Auth credentials to R1, exactly like an SSH login.

• response.json(): Converts the JSON response body into a Python dict so you can print it.

If R1 accepts the request, response.status_code returns 200 and the parsed dictionary appears.

Script 1 fetched one interface and printed the whole dictionary.
Real scripts dig into that dictionary, and they plan for the day R1 does not answer.

Script 2 — Parse and Loop Through Interfaces

This is the kind of script you will see in an exam exhibit.
It fetches every interface from R1 and prints each name with its type:

import requests
import urllib3
urllib3.disable_warnings()

url = "https://192.168.1.1/restconf/data/ietf-interfaces:interfaces"
headers = {"Accept": "application/yang-data+json"}

response = requests.get(url, headers=headers,
                        auth=("admin", "cisco123"),
                        verify=False)

data = response.json()

for iface in data["ietf-interfaces:interfaces"]["interface"]:
    print(iface["name"], iface["type"])

Output:

GigabitEthernet0/1 iana-if-type:ethernetCsmacd
GigabitEthernet0/2 iana-if-type:ethernetCsmacd
Loopback0 iana-if-type:softwareLoopback

Trace what happens after the response arrives:

• response.json(): Converts the raw JSON body into a nested Python dictionary.

• data["ietf-interfaces:interfaces"]: Navigates one level deep into the container.

• ["interface"]: Returns the list of interface dictionaries.

• for loop: Walks each dictionary and prints its name and type keys.

Exam questions often show this script and ask: "What is achieved by this script?"
Your job is to trace the keys until you reach the printed value.