F5 root password change via python script issues

i would suggest using the REST API available with F5 devices for automation, instead of using paramiko, you can use paramiko in use cases were a REST API is not availbe, for changing the root password an API is already availble you can refer to this

Sample code below:

>>> import requests
>>> import json
>>> requests.packages.urllib3.disable_warnings()
>>> b = requests.session()
>>> b.auth = ('admin', 'password')
>>> b.verify = False
>>> b.headers.update({'Content-Type':'application/json'})
>>> payload = { }
>>> payload['oldPassword'] = "password"
>>> payload['newPassword'] = "password1"
>>> b.post('https://192.168.190.130/mgmt/shared/authn/root', data=json.dumps(payload))