homework 4.2: add question 4

src/homework/04-script/4.2/q4.py

@@ -0,0 +1,40 @@
+#!/usr/bin/env python3
+
+import json
+import io
+import socket
+
+filename = 'hosts.json'
+
+hostsList = {
+    "drive.google.com",
+    "mail.google.com",
+    "google.com"
+}
+
+with open(filename, 'r+') as file:
+    jsonStr = file.read()
+    try:
+        jsonObj = json.load(io.StringIO(jsonStr))
+    except BaseException as err:
+        jsonObj = dict({})
+        print('error {}'.format(err))
+        exit(1)
+
+    file.truncate(0)
+    file.seek(0)
+
+    for hostname in hostsList:
+        ipAddr = socket.gethostbyname(hostname)
+        prevIpAddr = jsonObj.get(hostname)
+
+        if prevIpAddr is None or prevIpAddr == '':
+            prevIpAddr = ipAddr
+
+        print('{} - {}'.format(hostname, ipAddr))
+        if ipAddr != prevIpAddr:
+            print('[ERROR] {} IP mismatch: {} {}'.format(hostname, ipAddr, prevIpAddr))
+
+        jsonObj[hostname] = ipAddr
+
+    file.write(json.dumps(jsonObj))