From d5363e8045f1f810d187e50df8ea6f274de1f249 Mon Sep 17 00:00:00 2001
From: Sachi King <nakato@nakato.io>
Date: Mon, 27 Jun 2022 10:50:05 +1000
Subject: [PATCH] Add comments and use list comprehensions

Per PR review, use list comprehensions as they are prefered in py3 over
use of filter.

Add comments to describe the building of the zone tree.
---
 octodns/manager.py | 17 +++++++++++++----
 octodns/zone.py    |  3 +--
 2 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/octodns/manager.py b/octodns/manager.py
index 27b384d..030298e 100644
--- a/octodns/manager.py
+++ b/octodns/manager.py
@@ -167,12 +167,15 @@ class Manager(object):
         # reparent children to their parent zone from the tree root.
         for name in sorted(self.config['zones'].keys(),
                            key=lambda s: 0 - s.count('.')):
+            # Trim the trailing dot from FQDN
             name = name[:-1]
             this = {}
-            for sz in filter(
-                lambda k: k.endswith(name), set(zone_tree.keys())
-            ):
+            for sz in [k for k in zone_tree.keys() if k.endswith(name)]:
+                # Found a zone in tree root that is our child, slice the
+                # name and move its tree under ours.
                 this[sz[:-(len(name) + 1)]] = zone_tree.pop(sz)
+            # Add to tree root where it will be reparented as we iterate up
+            # the tree.
             zone_tree[name] = this
         self.zone_tree = zone_tree
 
@@ -272,11 +275,17 @@ class Manager(object):
         name = zone_name[:-1]
         where = self.zone_tree
         while True:
-            parent = next(filter(lambda k: name.endswith(k), where), None)
+            # Find parent if it exists
+            parent = next((k for k in where if name.endswith(k)), None)
             if not parent:
+                # The zone_name in the tree has been reached, stop searching.
                 break
+            # Move down the tree and slice name to get the remainder for the
+            # next round of the search.
             where = where[parent]
             name = name[:-(len(parent) + 1)]
+        # `where` is now pointing at the dictionary of children for zone_name
+        # in the tree
         sub_zone_names = where.keys()
         self.log.debug('configured_sub_zones: subs=%s', sub_zone_names)
         return set(sub_zone_names)
diff --git a/octodns/zone.py b/octodns/zone.py
index 41cd6ec..7e42fa3 100644
--- a/octodns/zone.py
+++ b/octodns/zone.py
@@ -69,8 +69,7 @@ class Zone(object):
 
         name = record.name
 
-        if not lenient and any(map(lambda sz: name.endswith(sz),
-                                   self.sub_zones)):
+        if not lenient and any((name.endswith(sz) for sz in self.sub_zones)):
             if name not in self.sub_zones:
                 # it's a record for something under a sub-zone
                 raise SubzoneRecordException(f'Record {record.fqdn} is under '