SF bug 1065388: calendar day/month name lookup too slow

__getitem__() methods:  compute only the new spellings needed to satisfy
the given indexing object.  This is purely an optimization (it should
have no effect on visible semantics).

2 files changed, 24 insertions, 16 deletions

diff --git a/Lib/calendar.py b/Lib/calendar.py
index c2a9775ebf..70813896d1 100644
--- a/Lib/calendar.py
+++ b/Lib/calendar.py
@@ -28,27 +28,37 @@ mdays = [0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]
 # fresh on each call, in case the user changes locale between calls.
 
 class _localized_month:
+
+    _months = [datetime.date(2001, i+1, 1).strftime for i in range(12)]
+    _months.insert(0, lambda x: "")
+
     def __init__(self, format):
         self.format = format
 
     def __getitem__(self, i):
-        data = [datetime.date(2001, j, 1).strftime(self.format)
-                     for j in range(1, 13)]
-        data.insert(0, "")
-        return data[i]
+        funcs = self._months[i]
+        if isinstance(i, slice):
+            return [f(self.format) for f in funcs]
+        else:
+            return funcs(self.format)
 
     def __len__(self):
         return 13
 
 class _localized_day:
+
+    # January 1, 2001, was a Monday.
+    _days = [datetime.date(2001, 1, i+1).strftime for i in range(7)]
+
     def __init__(self, format):
         self.format = format
 
     def __getitem__(self, i):
-        # January 1, 2001, was a Monday.
-        data = [datetime.date(2001, 1, j+1).strftime(self.format)
-                     for j in range(7)]
-        return data[i]
+        funcs = self._days[i]
+        if isinstance(i, slice):
+            return [f(self.format) for f in funcs]
+        else:
+            return funcs(self.format)
 
     def __len__(self):
         return 7
diff --git a/Lib/test/test_calendar.py b/Lib/test/test_calendar.py
index 2dc486fee8..34d365b25a 100644
--- a/Lib/test/test_calendar.py
+++ b/Lib/test/test_calendar.py
@@ -37,10 +37,9 @@ class CalendarTestCase(unittest.TestCase):
             self.assertEqual(len(value), 7)
             self.assertEqual(len(value[:]), 7)
             # ensure they're all unique
-            d = {}
-            for v in value:
-                d[v] = 1
-            self.assertEqual(len(d), 7)
+            self.assertEqual(len(set(value)), 7)
+            # verify it "acts like a sequence" in two forms of iteration
+            self.assertEqual(value[::-1], list(reversed(value)))
 
     def test_months(self):
         for attr in "month_name", "month_abbr":
@@ -49,10 +48,9 @@ class CalendarTestCase(unittest.TestCase):
             self.assertEqual(len(value[:]), 13)
             self.assertEqual(value[0], "")
             # ensure they're all unique
-            d = {}
-            for v in value:
-                d[v] = 1
-            self.assertEqual(len(d), 13)
+            self.assertEqual(len(set(value)), 13)
+            # verify it "acts like a sequence" in two forms of iteration
+            self.assertEqual(value[::-1], list(reversed(value)))
 
 
 class MonthCalendarTestCase(unittest.TestCase):