Exception handling for wrong device

netst.src/netst.py

 import sys
 import time
 
+interfaces = ifcfg.interfaces()
+
+def exit_device():
+    print("Possible devices:", ", ".join(interfaces.keys()))
+    sys.exit(1)
+
+
 def gateway(device):
     with open("/proc/net/route") as fh:
         # skip header
 try:
     DEVICE = sys.argv[1]
 except IndexError:
-    print("You need to give the device name as first argument")
-    sys.exit()
+    print("You need to give the device name as first argument!\n")
+    exit_device()
 
 HRN = {     # Human Readable Name
     'MAC': 'ether',
 }
 
 try:
-    info = ifcfg.interfaces()[DEVICE]
+    info = interfaces[DEVICE]
 except KeyError:
-    print("Unknown device:", DEVICE)
-    sys.exit(1)
+    print("Unknown device:", DEVICE, "\n")
+    exit_device()
 try:
     dns_resolver = dns.resolver.Resolver()
 except dns.resolver.NoResolverConfiguration: