Refactor calculation of the cache key. Minor code cleanups.
diff --git a/Lib/functools.py b/Lib/functools.py
index 7fc42af..adc7927 100644
--- a/Lib/functools.py
+++ b/Lib/functools.py
@@ -146,31 +146,35 @@
# The internals of the lru_cache are encapsulated for thread safety and
# to allow the implementation to change (including a possible C version).
- def decorating_function(user_function,
- *, tuple=tuple, sorted=sorted, map=map, len=len, type=type):
+ def decorating_function(user_function):
cache = dict()
hits = misses = 0
- cache_get = cache.get # bound method for fast lookup
- kwd_mark = (object(),) # separates positional and keyword args
- lock = Lock() # needed because linkedlist isn't threadsafe
- root = [] # root of circular doubly linked list
+ cache_get = cache.get # bound method to lookup key or return None
+ _len = len # localize the global len() function
+ kwd_mark = (object(),) # separate positional and keyword args
+ lock = Lock() # because linkedlist updates aren't threadsafe
+ root = [] # root of the circular doubly linked list
root[:] = [root, root, None, None] # initialize by pointing to self
- PREV, NEXT, KEY, RESULT = 0, 1, 2, 3 # names of link fields
+ PREV, NEXT, KEY, RESULT = 0, 1, 2, 3 # names for the link fields
+
+ def make_key(args, kwds, typed, tuple=tuple, sorted=sorted, type=type):
+ key = args
+ if kwds:
+ sorted_items = tuple(sorted(kwds.items()))
+ key += kwd_mark + sorted_items
+ if typed:
+ key += tuple(type(v) for v in args)
+ if kwds:
+ key += tuple(type(v) for k, v in sorted_items)
+ return key
if maxsize is None:
@wraps(user_function)
def wrapper(*args, **kwds):
# simple caching without ordering or size limit
nonlocal hits, misses
- key = args
- if kwds:
- 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)
+ key = make_key(args, kwds, typed) if kwds or typed else args
result = cache_get(key)
if result is not None:
hits += 1
@@ -184,14 +188,7 @@
def wrapper(*args, **kwds):
# size limited caching that tracks accesses by recency
nonlocal hits, misses
- key = args
- if kwds:
- 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)
+ key = make_key(args, kwds, typed) if kwds or typed else args
with lock:
link = cache_get(key)
if link is not None:
@@ -210,7 +207,7 @@
last = root[PREV]
link = [last, root, key, result]
cache[key] = last[NEXT] = root[PREV] = link
- if len(cache) > maxsize:
+ if _len(cache) > maxsize:
# purge least recently used cache entry
old_prev, old_next, old_key, old_result = root[NEXT]
root[NEXT] = old_next
@@ -229,7 +226,6 @@
nonlocal hits, misses, root
with lock:
cache.clear()
- root = []
root[:] = [root, root, None, None]
hits = misses = 0