Issue 13227: Option to make the lru_cache() type specific (suggested by Andrew Koenig).

1 files changed, 18 insertions, 4 deletions

diff --git a/Lib/functools.py b/Lib/functools.py
index 038f284..1abb37a 100644
--- a/Lib/functools.py
+++ b/Lib/functools.py
@@ -121,12 +121,16 @@ except ImportError:
 
 _CacheInfo = namedtuple("CacheInfo", "hits misses maxsize currsize")
 
-def lru_cache(maxsize=100):
+def lru_cache(maxsize=100, typed=False):
     """Least-recently-used cache decorator.
 
     If *maxsize* is set to None, the LRU features are disabled and the cache
     can grow without bound.
 
+    If *typed* is True, arguments of different types will be cached separately.
+    For example, f(3.0) and f(3) will be treated as distinct calls with
+    distinct results.
+
     Arguments to the cached function must be hashable.
 
     View the cache statistics named tuple (hits, misses, maxsize, currsize) with
@@ -142,7 +146,7 @@ def lru_cache(maxsize=100):
     # to allow the implementation to change (including a possible C version).
 
     def decorating_function(user_function,
-                tuple=tuple, sorted=sorted, len=len, KeyError=KeyError):
+            *, tuple=tuple, sorted=sorted, map=map, len=len, type=type, KeyError=KeyError):
 
         hits = misses = 0
         kwd_mark = (object(),)          # separates positional and keyword args
@@ -156,7 +160,12 @@ def lru_cache(maxsize=100):
                 nonlocal hits, misses
                 key = args
                 if kwds:
-                    key += kwd_mark + tuple(sorted(kwds.items()))
+                    sorted_items = tuple(sorted(kwds.items()))
+                    key += kwd_mark + sorted_items
+                if typed:
+                    key += tuple(map(type, args))
+                    if kwds:
+                        key += tuple(type(v) for k, v in sorted_items)
                 try:
                     result = cache[key]
                     hits += 1
@@ -177,7 +186,12 @@ def lru_cache(maxsize=100):
                 nonlocal hits, misses
                 key = args
                 if kwds:
-                    key += kwd_mark + tuple(sorted(kwds.items()))
+                    sorted_items = tuple(sorted(kwds.items()))
+                    key += kwd_mark + sorted_items
+                if typed:
+                    key += tuple(map(type, args))
+                    if kwds:
+                        key += tuple(type(v) for k, v in sorted_items)
                 with lock:
                     try:
                         result = cache[key]