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Issue 10593: Adopt Nick's suggestion for an lru_cache with maxsize=None.

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This commit is contained in:
Raymond Hettinger 2010-12-01 03:45:41 +00:00
parent ed3a7d2d60
commit c79fb0e52d
3 changed files with 79 additions and 26 deletions
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60
Lib/functools.py
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@ -119,6 +119,9 @@ _CacheInfo = namedtuple("CacheInfo", "hits misses maxsize currsize")
def lru_cache(maxsize=100):
"""Least-recently-used cache decorator.
If *maxsize* is set to None, the LRU features are disabled and the cache
can grow without bound.
Arguments to the cached function must be hashable.
View the cache statistics named tuple (hits, misses, maxsize, currsize) with
@ -136,32 +139,51 @@ def lru_cache(maxsize=100):
def decorating_function(user_function,
tuple=tuple, sorted=sorted, len=len, KeyError=KeyError):
cache = OrderedDict() # ordered least recent to most recent
cache_popitem = cache.popitem
cache_renew = cache.move_to_end
hits = misses = 0
kwd_mark = object() # separates positional and keyword args
lock = Lock()
@wraps(user_function)
def wrapper(*args, **kwds):
nonlocal hits, misses
key = args
if kwds:
key += (kwd_mark,) + tuple(sorted(kwds.items()))
try:
with lock:
if maxsize is None:
cache = dict() # simple cache without ordering or size limit
@wraps(user_function)
def wrapper(*args, **kwds):
nonlocal hits, misses
key = args
if kwds:
key += (kwd_mark,) + tuple(sorted(kwds.items()))
try:
result = cache[key]
cache_renew(key) # record recent use of this key
hits += 1
except KeyError:
result = user_function(*args, **kwds)
with lock:
cache[key] = result # record recent use of this key
except KeyError:
result = user_function(*args, **kwds)
cache[key] = result
misses += 1
if len(cache) > maxsize:
cache_popitem(0) # purge least recently used cache entry
return result
return result
else:
cache = OrderedDict() # ordered least recent to most recent
cache_popitem = cache.popitem
cache_renew = cache.move_to_end
@wraps(user_function)
def wrapper(*args, **kwds):
nonlocal hits, misses
key = args
if kwds:
key += (kwd_mark,) + tuple(sorted(kwds.items()))
try:
with lock:
result = cache[key]
cache_renew(key) # record recent use of this key
hits += 1
except KeyError:
result = user_function(*args, **kwds)
with lock:
cache[key] = result # record recent use of this key
misses += 1
if len(cache) > maxsize:
cache_popitem(0) # purge least recently used cache entry
return result
def cache_info():
"""Report cache statistics"""