[sflow] Fix traceback seen for show sflow interface (sonic-net#1282)

Fixed a traceback seen when show sflow interface is executed.
Updated the script to follow Python3 conventions.

Signed-off-by: Garrick He <garrick_he@dell.com>

show/sflow.py

@@ -50,11 +50,12 @@ def show_sflow_interface(config_db):
     for pname in natsorted(list(port_tbl.keys())):
         intf_key = 'SFLOW_SESSION_TABLE:' + pname
         sess_info = sess_db.get_all(sess_db.APPL_DB, intf_key)
-        if sess_info is None:
+        if (sess_info is None or sess_info.get('admin_state') is None or
+            sess_info.get('sample_rate') is None):
             continue
         body_info = [pname]
-        body_info.append(sess_info['admin_state'])
-        body_info.append(sess_info['sample_rate'])
+        body_info.append(sess_info.get('admin_state'))
+        body_info.append(sess_info.get('sample_rate'))
         body.append(body_info)
     click.echo(tabulate(body, header, tablefmt='grid'))
 

tests/mock_tables/appl_db.json

@@ -15,6 +15,15 @@
         "admin_state": "up",
         "sample_rate": "5000"
     },
+    "SFLOW_SESSION_TABLE:Ethernet8": {
+        "BAD": "BAD"
+    },
+    "SFLOW_SESSION_TABLE:Ethernet12": {
+        "sample_rate": "5000"
+    },
+    "SFLOW_SESSION_TABLE:Ethernet16": {
+        "admin_state": "up"
+    },
     "PORT_TABLE:Ethernet0": {
         "index": "0",
         "lanes": "0",

tests/sflow_test.py

@@ -261,6 +261,35 @@ def test_config_sflow_intf_sample_rate(self):
 
         return
 
+    def test_config_disable_all_intf(self):
+        db = Db()
+        runner = CliRunner()
+        obj = {'db':db.cfgdb}
+
+        # disable all interfaces
+        result = runner.invoke(config.config.commands["sflow"].
+            commands["interface"].commands["disable"], ["all"], obj=obj)
+        print(result.exit_code, result.output)
+        assert result.exit_code == 0
+
+        # verify in configDb
+        sflowSession = db.cfgdb.get_table('SFLOW_SESSION')
+        assert sflowSession["all"]["admin_state"] == "down"
+
+    def test_config_enable_all_intf(self):
+        db = Db()
+        runner = CliRunner()
+        obj = {'db':db.cfgdb}
+        # enable all interfaces
+        result = runner.invoke(config.config.commands["sflow"].commands["interface"].
+                               commands["enable"], ["all"], obj=obj)
+        print(result.exit_code, result.output)
+        assert result.exit_code == 0
+
+        # verify in configDb
+        sflowSession = db.cfgdb.get_table('SFLOW_SESSION')
+        assert sflowSession["all"]["admin_state"] == "up"
+
     @classmethod
     def teardown_class(cls):
         print("TEARDOWN")