examples/ytfeed.aggregate: better documentation

examples/ytfeed.aggregate

@@ -4,13 +4,14 @@ import re, sys, xml.etree.ElementTree as ET
 ET.register_namespace("",      "http://www.w3.org/2005/Atom")
 ET.register_namespace("media", "http://search.yahoo.com/mrss/")
 ET.register_namespace("yt",    "http://www.youtube.com/xml/schemas/2015")
-def sortby(entry):
-    return entry.findall("{http://www.w3.org/2005/Atom}published")[0].text
 macrofeed = ET.Element('feed')
 macrofeed.extend(
     sorted([
             entry
-            # Split the input by file.
+            # Split the input by file. This relies on a typical <XML /> tag
+            # starting a file. Theoretically this assumption could be wrong,
+            # but in that case the XML parser would break before
+            # ytfeed.aggregate could spit malformed output.
             for feed in re.split(r'<\?xml.*?\?>', sys.stdin.read())[1:]
             # Get the entries out of each file.
             for entry
@@ -18,9 +19,8 @@ macrofeed.extend(
                     .findall("{http://www.w3.org/2005/Atom}entry")
         ],
         # Gets the publication date and sorts the entries from old to new.
-        key = lambda entry
+        key = lambda entry # (this is a text sort but it still works)
            : entry.findall("{http://www.w3.org/2005/Atom}published")[0].text,
-        reverse = False # toggle this to switch the order
     )
 )
 print(ET.tostring(macrofeed, encoding="unicode"))