Fix #292, fix #205, fix #103: TTLCache.expire() returns iterable of e…

…xpired (key, value) pairs.

src/cachetools/__init__.py

@@ -26,7 +26,6 @@
 
 
 class _DefaultSize:
-
     __slots__ = ()
 
     def __getitem__(self, _):
@@ -378,7 +377,6 @@ class TTLCache(_TimedCache):
     """LRU Cache implementation with per-item time-to-live (TTL) value."""
 
     class _Link:
-
         __slots__ = ("key", "expires", "next", "prev")
 
         def __init__(self, key=None, expires=None):
@@ -469,19 +467,25 @@ def ttl(self):
         return self.__ttl
 
     def expire(self, time=None):
-        """Remove expired items from the cache."""
+        """Remove expired items from the cache and return an iterable of
+        expired `(key, value)` pairs).
+        """
         if time is None:
             time = self.timer()
         root = self.__root
         curr = root.next
         links = self.__links
+        expired = []
         cache_delitem = Cache.__delitem__
+        cache_getitem = Cache.__getitem__
         while curr is not root and not (time < curr.expires):
+            expired.append((curr.key, cache_getitem(self, curr.key)))
             cache_delitem(self, curr.key)
             del links[curr.key]
             next = curr.next
             curr.unlink()
             curr = next
+        return expired
 
     def popitem(self):
         """Remove and return the `(key, value)` pair least recently used that
@@ -508,7 +512,6 @@ class TLRUCache(_TimedCache):
 
     @functools.total_ordering
     class _Item:
-
         __slots__ = ("key", "expires", "removed")
 
         def __init__(self, key=None, expires=None):

tests/test_ttl.py

@@ -26,7 +26,6 @@ def __init__(self, maxsize, ttl=math.inf, **kwargs):
 
 
 class TTLCacheTest(unittest.TestCase, CacheTestMixin):
-
     Cache = TTLTestCache
 
     def test_ttl(self):
@@ -132,28 +131,32 @@ def test_ttl_expire(self):
         self.assertEqual(2, cache[2])
         self.assertEqual(3, cache[3])
 
-        cache.expire()
+        items = cache.expire()
+        self.assertEqual(set(), set(items))
         self.assertEqual({1, 2, 3}, set(cache))
         self.assertEqual(3, len(cache))
         self.assertEqual(1, cache[1])
         self.assertEqual(2, cache[2])
         self.assertEqual(3, cache[3])
 
-        cache.expire(3)
+        items = cache.expire(3)
+        self.assertEqual({(1, 1)}, set(items))
         self.assertEqual({2, 3}, set(cache))
         self.assertEqual(2, len(cache))
         self.assertNotIn(1, cache)
         self.assertEqual(2, cache[2])
         self.assertEqual(3, cache[3])
 
-        cache.expire(4)
+        items = cache.expire(4)
+        self.assertEqual({(2, 2)}, set(items))
         self.assertEqual({3}, set(cache))
         self.assertEqual(1, len(cache))
         self.assertNotIn(1, cache)
         self.assertNotIn(2, cache)
         self.assertEqual(3, cache[3])
 
-        cache.expire(5)
+        items = cache.expire(5)
+        self.assertEqual({(3, 3)}, set(items))
         self.assertEqual(set(), set(cache))
         self.assertEqual(0, len(cache))
         self.assertNotIn(1, cache)
@@ -192,7 +195,9 @@ def test_ttl_datetime(self):
 
         cache[1] = 1
         self.assertEqual(1, len(cache))
-        cache.expire(datetime.now())
+        items = cache.expire(datetime.now())
+        self.assertEqual([], list(items))
         self.assertEqual(1, len(cache))
-        cache.expire(datetime.now() + timedelta(days=1))
+        items = cache.expire(datetime.now() + timedelta(days=1))
+        self.assertEqual([(1, 1)], list(items))
         self.assertEqual(0, len(cache))