refactor and add explanatory commments & links

hughlilly · hughlilly · commit b7360e9b133d · 2022-02-04T12:32:06.000+13:00
diff --git a/07-files/files7.py b/07-files/files7.py
@@ -8,22 +8,28 @@
 after_file = Path('./data/ALA_after.csv')
 outfile = Path('./data/ALA_diff.csv')
 
+# Create a set object by mapping the "before" file onto a tuple object
+# (an immutable list), passing teh result of `open()` to `csv.reader()`
 before = set(
     map(
         tuple,
         csv.reader(open(before_file))
     )
 )
 
+# Repeat for the second ("after") file
 after = set(map(tuple, csv.reader(open(after_file))))
 
+# Use the caret (^) operator to get the symmetric difference between the sets
+# https://www.linuxtopia.org/online_books/programming_books/python_programming/python_ch16s03.html
+
 differences = before ^ after
 
 output = csv.writer(open(outfile, mode='w'))
 
 compared = sorted(differences, key=lambda x: x[0], reverse=True)
 
-for iter, row in enumerate():
+for count, row in enumerate():
     output.writerow(row)
 
-print(f"Wrote {iter} rows to output file.")
+print(f"Wrote {count} rows to output file.")
