Lists in Dictionaries Assistance

[buran]

here is more general example that will create a dict with devices for each department
note that in your data 'department' is a list, even with one value. I don't know if it is possible to have more than one department in this list

import yaml
from collections import defaultdict
     
with open('router.cfg', 'r') as lb:
    try:
        test = (yaml.load(lb))
    except yaml.YAMLError as exc:
        print(exc)
    
maindict = test['device_list']
devices = defaultdict(list)
for location in maindict.values():
    for department in location['department']:
        devices[department].extend(location['devices']) 

print(devices)
print(devices['FIN'])

this could be shortened with list comprehension but now is more explicit