Q: Converting hostname to IP from a dictionary for netmiko connection? - python-2.7

Question

In the past, I was able to do something simple like this to read a file
of IP addresses that I would iterate through to SSH to each one
# Grab the list of devices from a text file
devices = open('./devices.txt','r').read().split('\n')
# Connect to each router and do a show run command
for device in devices:
net_connect = ConnectHandler(device_type="cisco_ios", ip=device, username="myusername",
password=password)
This time, however, I need to do something a bit more complex.
I pull some data from a JSON source where I can derive a "hostname."
But I cannot connect to the "hostname." If the hostnames were in DNS
that would be easier but sadly they are not.
So.. I have a list of hosts to IPs that I figured I could use and pull
into a dictionary.
But now I somehow need to match up the hostname that gets derived from
the JSON data to match against a switchname in the hosts.csv so that I can
then basically convert hostname to IP so that I can then iterate through each
device in devices to SSH into each one.
This is all I have so far. I'm stuck at this point. Not sure how to match
things up to get the IP to use in my net_connect statement.
# Creat dict mapping hostnames to IP address for devices
with open(r'hosts.csv', 'r') as f:
for line in f:
switch = {}
switch_line = line.split(',')
switch = {
'ip': switch_line[1],
'switchname': str(switch_line[0]).strip('\n')
# Define list of devices to connect to and the config changes to be made
pa = []
# This data is coming from a JSON source
for device in devices:
if device['switchParent']:
hostname = device['switchParent']
else:
hostname = device['destDevice']
# hostname technically is the device I need to connect
# however it needs to resolve to an IP from the switch dict earlier
net_connect = ConnectHandler(device_type="cisco_ios", ip=hostname,
username="myusername", password=password)

Answer 1

Assuming that switchname has a unique ip address then you should parse the hosts.csv file this way:
# Create dict mapping hostnames to IP address for devices
switch = {}
with open(r'hosts.csv', 'r') as f:
for line in f:
switch_line = line.split(',')
switch[str(switch_line[0].strip())] = switch_line[1]
Then you go through the JSON data source:
# This data is coming from a JSON source
for device in devices:
if device['switchParent']:
hostname = device['switchParent']
else:
hostname = device['destDevice']
# hostname technically is the device I need to connect
# however it needs to resolve to an IP from the switch dict earlier
net_connect = ConnectHandler(device_type="cisco_ios", ip=switch[hostname],
username="myusername", password=password)
That should work IF hostname is expected to be one of the keys from the switch dict.