💡
A virtual environment is an isolated Python workspace where you can install packages without affecting the system-wide Python installation
## The Complete Script
Here is the full working script before we break it down line by line. Read it once, then follow the steps below to understand exactly what each part does.
```python
from nornir import InitNornir
from nornir_netmiko.tasks import netmiko_send_config
from nornir_utils.plugins.functions import print_result
from nornir.core.task import Result
from netmiko import ConnectHandler
from datetime import datetime
nr = InitNornir(config_file="config.yaml")
def deploy_services(task):
device = {
"device_type": "nokia_sros",
"host": task.host.hostname,
"username": task.host.username,
"password": task.host.password,
"secret": "",
}
commands = [
"configure",
" system",
" time",
" ntp",
" server 192.168.1.1",
" no shutdown",
" exit",
" exit",
" exit",
"exit",
]
with ConnectHandler(**device) as conn:
output = conn.send_config_set(commands)
print(f"[{task.host.name}] Output:\n{output}")
verify = conn.send_command("show system ntp")
print(f"[{task.host.name}] Verification:\n{verify}")
return Result(host=task.host, result=output, changed=True)
start_time = datetime.now()
results = nr.run(task=deploy_services)
end_time = datetime.now()
print_result(results)
print(f"Execution Time: {end_time - start_time}")
```
### Step-by-step breakdown
1\. **Import the Libraries**
```python
from nornir import InitNornir
from nornir_netmiko.tasks import netmiko_send_config
from nornir_utils.plugins.functions import print_result
from nornir.core.task import Result
from netmiko import ConnectHandler
from datetime import datetime
```
`InitNornir` loads the framework and inventory. `netmiko_send_config` is the Nornir plugin task for pushing config — imported but not used directly in this script (we bypass it with raw ConnectHandler instead, due to a `nornir-netmiko` bug with Nokia SROS **24.10.R5** discovered while testing). `print_result` gives a formatted per-host output table. `Result` is the object we return from our task to tell Nornir what happened. `ConnectHandler` is Netmiko's core SSH connection class. `datetime` is used to measure total execution time
2\. **Initialise Nornir from config file**
```python
nr = InitNornir(config_file="config.yaml")
```
This single line reads `config.yaml` and builds the entire Nornir runtime: the inventory (hosts.yaml + groups.yaml), the runner (ThreadedRunner with 10 workers).
3\. **Define the task function**
```python
def deploy_services(task):
```
This is a Nornir task — a plain Python function that accepts a single argument called task. Nornir calls this function once per host in your inventory, passing a Task object. Nornir uses threads, this function runs simultaneously across all hosts.
4\. **Build the device connection dictionary**
```python
device = {
"device_type": "nokia_sros",
"host": task.host.hostname,
"username": task.host.username,
"password": task.host.password,
"secret": "",
}
```
This dictionary is passed directly to Netmiko's ConnectHandler. device\_type tells Netmiko which SSH driver to use — nokia\_sros loads the Nokia-specific handler that understands SROS prompts and CLI behaviour.
5\. **Define the CLI commands**
```python
commands = [
"configure",
" system",
" time",
" ntp",
" server 192.168.1.1",
" no shutdown",
" exit",
" exit",
" exit",
"exit",
]
```
In this example Nokia SROS Classic CLI uses a hierarchical config tree. You must navigate down into each level with the context keyword (configure, system, time, ntp) and then back out with exit at each level.
6\. **Open the SSH connection with ConnectHandler**
```python
with ConnectHandler(**device) as conn:
```
ConnectHandler(\*\*device) unpacks the device dictionary as keyword arguments and opens an SSH session to the router. Using `ConnectHandler` directly (rather than through nornir-netmiko) bypasses the plugin bug where extras from the Nornir inventory were not being passed through to `ConnectHandler`.
7\. **Send the configuration commands**
```python
output = conn.send_config_set(commands)
print(f"[{task.host.name}] Output:\n{output}")
```
`send_config_set()` sends each command in the list one by one over SSH and captures the router's response after each command. For SROS it handles the prompt detection automatically — it waits for the next prompt before sending the next command. The print statement immediately shows what the router returned
8\. **Verify the configuration was applied**
```python
verify = conn.send_command("show system ntp")
print(f"[{task.host.name}] Verification:\n{verify}")
```
`send_command()` sends a single show command and returns the output as a string. Running show system ntp immediately after the config push confirms the NTP server is now present in the running config
9\. **Return a Result object to Nornir**
```python
return Result(host=task.host, result=output, changed=True)
```
Every Nornir task should return a Result object. `host=task.host` tells Nornir which device this result belongs to. `result=output` stores the raw command output in the result
10\. **Run the task across all hosts and measure time**
```python
start_time = datetime.now()
results = nr.run(task=deploy_services)
end_time = datetime.now()
```
`datetime.now()` captures the wall-clock time before and after execution
11\. **Print results and execution time**
```python
print_result(results)
print(f"Execution Time: {end_time - start_time}")
```
`print_result()` from nornir\_utils formats the AggregatedResult into the familiar Nornir output tree
### Execution Output
```python
[router1] Output:
configure
A:PE1>config# system
A:PE1>config>system# time
A:PE1>config>system>time# ntp
A:PE1>config>system>time>ntp# server 192.168.1.1
*A:PE1>config>system>time>ntp# no shutdown
*A:PE1>config>system>time>ntp# exit
*A:PE1>config>system>time# exit
*A:PE1>config>system# exit
*A:PE1>config# exit
*A:PE1# exit all
*A:PE1#
[router1] Verification:
===============================================================
NTP Status
===============================================================
Configured : Yes Stratum : -
Admin Status : up Oper Status : up
Server Enabled : No Server Authenticate : No
Clock Source : none
Auth Check : Yes
Auth Keychain :
Current Date & Time: 2026/04/14 00:14:27 UTC
===============================================================
deploy_services************************************************
* router1 ** changed : True ***********************************
vvvv deploy_services ** changed : True vvvvvvvvvvvvvvvvvvv INFO
configure
A:PE1>config# system
A:PE1>config>system# time
A:PE1>config>system>time# ntp
A:PE1>config>system>time>ntp# server 192.168.1.1
*A:PE1>config>system>time>ntp# no shutdown
*A:PE1>config>system>time>ntp# exit
*A:PE1>config>system>time# exit
*A:PE1>config>system# exit
*A:PE1>config# exit
*A:PE1# exit all
*A:PE1#
^^^^ END deploy_services ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
```