From 7e0c581c49b0945661089365160e0aef423dfba7 Mon Sep 17 00:00:00 2001 From: Raymond Hettinger Date: Sat, 17 Mar 2012 15:10:24 -0700 Subject: [PATCH] Low overhead path for maxsize==0 --- Lib/functools.py | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-) diff --git a/Lib/functools.py b/Lib/functools.py index f4c8271bc95..de30a921942 100644 --- a/Lib/functools.py +++ b/Lib/functools.py @@ -170,15 +170,16 @@ def lru_cache(maxsize=100, typed=False): cache = dict() hits = misses = 0 + kwd_mark = (object(),) # separate positional and keyword args 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 for the link fields def make_key(args, kwds, typed, tuple=tuple, sorted=sorted, type=type): + # helper function to build a cache key from positional and keyword args key = args if kwds: sorted_items = tuple(sorted(kwds.items())) @@ -189,7 +190,17 @@ def lru_cache(maxsize=100, typed=False): key += tuple(type(v) for k, v in sorted_items) return key - if maxsize is None: + if maxsize == 0: + + @wraps(user_function) + def wrapper(*args, **kwds): + # no caching, just do a statistics update after a successful call + nonlocal misses + result = user_function(*args, **kwds) + misses += 1 + return result + + elif maxsize is None: @wraps(user_function) def wrapper(*args, **kwds):