diff options
Diffstat (limited to 'Lib/functools.py')
| -rw-r--r-- | Lib/functools.py | 140 |
1 files changed, 103 insertions, 37 deletions
diff --git a/Lib/functools.py b/Lib/functools.py index 85ea257abd..ae4175d6a0 100644 --- a/Lib/functools.py +++ b/Lib/functools.py @@ -12,16 +12,22 @@ __all__ = ['update_wrapper', 'wraps', 'WRAPPER_ASSIGNMENTS', 'WRAPPER_UPDATES', 'total_ordering', 'cmp_to_key', 'lru_cache', 'reduce', 'partial'] from _functools import partial, reduce -from collections import OrderedDict, namedtuple +from collections import namedtuple try: from _thread import allocate_lock as Lock except: from _dummy_thread import allocate_lock as Lock + +################################################################################ +### update_wrapper() and wraps() decorator +################################################################################ + # update_wrapper() and wraps() are tools to help write # wrapper functions that can handle naive introspection -WRAPPER_ASSIGNMENTS = ('__module__', '__name__', '__doc__', '__annotations__') +WRAPPER_ASSIGNMENTS = ('__module__', '__name__', '__qualname__', '__doc__', + '__annotations__') WRAPPER_UPDATES = ('__dict__',) def update_wrapper(wrapper, wrapped, @@ -65,6 +71,11 @@ def wraps(wrapped, return partial(update_wrapper, wrapped=wrapped, assigned=assigned, updated=updated) + +################################################################################ +### total_ordering class decorator +################################################################################ + def total_ordering(cls): """Class decorator that fills in missing ordering methods""" convert = { @@ -93,6 +104,11 @@ def total_ordering(cls): setattr(cls, opname, opfunc) return cls + +################################################################################ +### cmp_to_key() function converter +################################################################################ + def cmp_to_key(mycmp): """Convert a cmp= function into a key= function""" class K(object): @@ -114,79 +130,128 @@ def cmp_to_key(mycmp): __hash__ = None return K -_CacheInfo = namedtuple("CacheInfo", "hits misses maxsize currsize") +try: + from _functools import cmp_to_key +except ImportError: + pass + + +################################################################################ +### LRU Cache function decorator +################################################################################ -def lru_cache(maxsize=100): +_CacheInfo = namedtuple("CacheInfo", ["hits", "misses", "maxsize", "currsize"]) + +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 - f.cache_info(). Clear the cache and statistics with f.cache_clear(). + View the cache statistics named tuple (hits, misses, maxsize, currsize) + with f.cache_info(). Clear the cache and statistics with f.cache_clear(). Access the underlying function with f.__wrapped__. See: http://en.wikipedia.org/wiki/Cache_algorithms#Least_Recently_Used """ + # Users should only access the lru_cache through its public API: # cache_info, cache_clear, and f.__wrapped__ # 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, len=len, KeyError=KeyError): + def decorating_function(user_function): + cache = {} hits = misses = 0 - kwd_mark = (object(),) # separates positional and keyword args - lock = Lock() # needed because OrderedDict isn't threadsafe + kwd_mark = (object(),) # separate positional and keyword args + cache_get = cache.get # bound method to lookup a key or return None + sentinel = object() # unique object used with cache_get + _len = len # localize the global len() function + 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 - if maxsize is None: - cache = dict() # simple cache without ordering or size limit + 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 + 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: + + def wrapper(*args, **kwds): + # no caching, just 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): + # simple caching without ordering or size limit nonlocal hits, misses - key = args - if kwds: - key += kwd_mark + tuple(sorted(kwds.items())) - try: - result = cache[key] + key = make_key(args, kwds, typed) if kwds or typed else args + result = cache_get(key, sentinel) + if result is not sentinel: hits += 1 return result - except KeyError: - pass result = user_function(*args, **kwds) cache[key] = result misses += 1 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())) + # size limited caching that tracks accesses by recency + nonlocal root, hits, misses + key = make_key(args, kwds, typed) if kwds or typed else args with lock: - try: - result = cache[key] - cache_renew(key) # record recent use of this key + link = cache_get(key) + if link is not None: + # move the link to the front of the circular queue + link_prev, link_next, key, result = link + link_prev[NEXT] = link_next + link_next[PREV] = link_prev + last = root[PREV] + last[NEXT] = root[PREV] = link + link[PREV] = last + link[NEXT] = root hits += 1 return result - except KeyError: - pass result = user_function(*args, **kwds) with lock: - cache[key] = result # record recent use of this key + if _len(cache) < maxsize: + # put result in a new link at the front of the queue + last = root[PREV] + link = [last, root, key, result] + cache[key] = last[NEXT] = root[PREV] = link + else: + # use root to store the new key and result + root[KEY] = key + root[RESULT] = result + cache[key] = root + # empty the oldest link and make it the new root + root = root[NEXT] + del cache[root[KEY]] + root[KEY] = root[RESULT] = None misses += 1 - if len(cache) > maxsize: - cache_popitem(0) # purge least recently used cache entry return result def cache_info(): @@ -199,10 +264,11 @@ def lru_cache(maxsize=100): nonlocal hits, misses with lock: cache.clear() + root[:] = [root, root, None, None] hits = misses = 0 wrapper.cache_info = cache_info wrapper.cache_clear = cache_clear - return wrapper + return update_wrapper(wrapper, user_function) return decorating_function |