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Move make_key() out of the decorator body. Make keys that only need to be hashed once.

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Raymond Hettinger 2012-04-30 22:32:16 -07:00
parent 018b4fbb9b
commit 9acbb6074f
1 changed files with 27 additions and 17 deletions
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44
Lib/functools.py
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@ -142,6 +142,30 @@ except ImportError:
_CacheInfo = namedtuple("CacheInfo", ["hits", "misses", "maxsize", "currsize"]) _CacheInfo = namedtuple("CacheInfo", ["hits", "misses", "maxsize", "currsize"])
class _CacheKey(list):
'Make a cache key from optionally typed positional and keyword arguments'
__slots__ = 'hashvalue'
def __init__(self, args, kwds, typed,
kwd_mark = (object(),),
sorted=sorted, tuple=tuple, type=type, hash=hash):
key = args
if kwds:
sorted_items = sorted(kwds.items())
key += kwd_mark
for item in sorted_items:
key += item
if typed:
key += tuple(type(v) for v in args)
if kwds:
key += tuple(type(v) for k, v in sorted_items)
self[:] = key
self.hashvalue = hash(key) # so we only have to hash just once
def __hash__(self):
return self.hashvalue
def lru_cache(maxsize=100, typed=False): def lru_cache(maxsize=100, typed=False):
"""Least-recently-used cache decorator. """Least-recently-used cache decorator.
@ -168,8 +192,8 @@ def lru_cache(maxsize=100, typed=False):
# to allow the implementation to change (including a possible C version). # to allow the implementation to change (including a possible C version).
# Constants shared by all lru cache instances: # Constants shared by all lru cache instances:
kwd_mark = (object(),) # separate positional and keyword args
sentinel = object() # unique object used to signal cache misses sentinel = object() # unique object used to signal cache misses
make_key = _CacheKey # build a key from the function arguments
PREV, NEXT, KEY, RESULT = 0, 1, 2, 3 # names for the link fields PREV, NEXT, KEY, RESULT = 0, 1, 2, 3 # names for the link fields
def decorating_function(user_function): def decorating_function(user_function):
@ -182,20 +206,6 @@ def lru_cache(maxsize=100, typed=False):
root = [] # root of the circular doubly linked list root = [] # root of the circular doubly linked list
root[:] = [root, root, None, None] # initialize by pointing to self root[:] = [root, root, None, None] # initialize by pointing to self
def make_key(args, kwds, typed, tuple=tuple, sorted=sorted, type=type):
# build a cache key from positional and keyword args
key = args
if kwds:
sorted_items = tuple(sorted(kwds.items()))
key += kwd_mark
key += tuple(k for k, v in sorted_items)
key += tuple(v for k, v in 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 == 0: if maxsize == 0:
def wrapper(*args, **kwds): def wrapper(*args, **kwds):
@ -210,7 +220,7 @@ def lru_cache(maxsize=100, typed=False):
def wrapper(*args, **kwds): def wrapper(*args, **kwds):
# simple caching without ordering or size limit # simple caching without ordering or size limit
nonlocal hits, misses, currsize nonlocal hits, misses, currsize
key = make_key(args, kwds, typed) if kwds or typed else args key = make_key(args, kwds, typed)
result = cache_get(key, sentinel) result = cache_get(key, sentinel)
if result is not sentinel: if result is not sentinel:
hits += 1 hits += 1
@ -226,7 +236,7 @@ def lru_cache(maxsize=100, typed=False):
def wrapper(*args, **kwds): def wrapper(*args, **kwds):
# size limited caching that tracks accesses by recency # size limited caching that tracks accesses by recency
nonlocal root, hits, misses, currsize, full nonlocal root, hits, misses, currsize, full
key = make_key(args, kwds, typed) if kwds or typed else args key = make_key(args, kwds, typed)
with lock: with lock:
link = cache_get(key) link = cache_get(key)
if link is not None: if link is not None: