| """functools.py - Tools for working with functions and callable objects |
| """ |
| # Python module wrapper for _functools C module |
| # to allow utilities written in Python to be added |
| # to the functools module. |
| # Written by Nick Coghlan <ncoghlan at gmail.com> |
| # and Raymond Hettinger <python at rcn.com> |
| # Copyright (C) 2006-2010 Python Software Foundation. |
| # See C source code for _functools credits/copyright |
| |
| __all__ = ['update_wrapper', 'wraps', 'WRAPPER_ASSIGNMENTS', 'WRAPPER_UPDATES', |
| 'total_ordering', 'cmp_to_key', 'lru_cache', 'reduce', 'partial'] |
| |
| try: |
| from _functools import reduce |
| except ImportError: |
| pass |
| 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__', '__qualname__', '__doc__', |
| '__annotations__') |
| WRAPPER_UPDATES = ('__dict__',) |
| def update_wrapper(wrapper, |
| wrapped, |
| assigned = WRAPPER_ASSIGNMENTS, |
| updated = WRAPPER_UPDATES): |
| """Update a wrapper function to look like the wrapped function |
| |
| wrapper is the function to be updated |
| wrapped is the original function |
| assigned is a tuple naming the attributes assigned directly |
| from the wrapped function to the wrapper function (defaults to |
| functools.WRAPPER_ASSIGNMENTS) |
| updated is a tuple naming the attributes of the wrapper that |
| are updated with the corresponding attribute from the wrapped |
| function (defaults to functools.WRAPPER_UPDATES) |
| """ |
| wrapper.__wrapped__ = wrapped |
| for attr in assigned: |
| try: |
| value = getattr(wrapped, attr) |
| except AttributeError: |
| pass |
| else: |
| setattr(wrapper, attr, value) |
| for attr in updated: |
| getattr(wrapper, attr).update(getattr(wrapped, attr, {})) |
| # Return the wrapper so this can be used as a decorator via partial() |
| return wrapper |
| |
| def wraps(wrapped, |
| assigned = WRAPPER_ASSIGNMENTS, |
| updated = WRAPPER_UPDATES): |
| """Decorator factory to apply update_wrapper() to a wrapper function |
| |
| Returns a decorator that invokes update_wrapper() with the decorated |
| function as the wrapper argument and the arguments to wraps() as the |
| remaining arguments. Default arguments are as for update_wrapper(). |
| This is a convenience function to simplify applying partial() to |
| update_wrapper(). |
| """ |
| 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 = { |
| '__lt__': [('__gt__', lambda self, other: not (self < other or self == other)), |
| ('__le__', lambda self, other: self < other or self == other), |
| ('__ge__', lambda self, other: not self < other)], |
| '__le__': [('__ge__', lambda self, other: not self <= other or self == other), |
| ('__lt__', lambda self, other: self <= other and not self == other), |
| ('__gt__', lambda self, other: not self <= other)], |
| '__gt__': [('__lt__', lambda self, other: not (self > other or self == other)), |
| ('__ge__', lambda self, other: self > other or self == other), |
| ('__le__', lambda self, other: not self > other)], |
| '__ge__': [('__le__', lambda self, other: (not self >= other) or self == other), |
| ('__gt__', lambda self, other: self >= other and not self == other), |
| ('__lt__', lambda self, other: not self >= other)] |
| } |
| # Find user-defined comparisons (not those inherited from object). |
| roots = [op for op in convert if getattr(cls, op, None) is not getattr(object, op, None)] |
| if not roots: |
| raise ValueError('must define at least one ordering operation: < > <= >=') |
| root = max(roots) # prefer __lt__ to __le__ to __gt__ to __ge__ |
| for opname, opfunc in convert[root]: |
| if opname not in roots: |
| opfunc.__name__ = opname |
| opfunc.__doc__ = getattr(int, opname).__doc__ |
| 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): |
| __slots__ = ['obj'] |
| def __init__(self, obj): |
| self.obj = obj |
| def __lt__(self, other): |
| return mycmp(self.obj, other.obj) < 0 |
| def __gt__(self, other): |
| return mycmp(self.obj, other.obj) > 0 |
| def __eq__(self, other): |
| return mycmp(self.obj, other.obj) == 0 |
| def __le__(self, other): |
| return mycmp(self.obj, other.obj) <= 0 |
| def __ge__(self, other): |
| return mycmp(self.obj, other.obj) >= 0 |
| def __ne__(self, other): |
| return mycmp(self.obj, other.obj) != 0 |
| __hash__ = None |
| return K |
| |
| try: |
| from _functools import cmp_to_key |
| except ImportError: |
| pass |
| |
| |
| ################################################################################ |
| ### partial() argument application |
| ################################################################################ |
| |
| def partial(func, *args, **keywords): |
| """new function with partial application of the given arguments |
| and keywords. |
| """ |
| def newfunc(*fargs, **fkeywords): |
| newkeywords = keywords.copy() |
| newkeywords.update(fkeywords) |
| return func(*(args + fargs), **newkeywords) |
| newfunc.func = func |
| newfunc.args = args |
| newfunc.keywords = keywords |
| return newfunc |
| |
| try: |
| from _functools import partial |
| except ImportError: |
| pass |
| |
| |
| ################################################################################ |
| ### LRU Cache function decorator |
| ################################################################################ |
| |
| _CacheInfo = namedtuple("CacheInfo", ["hits", "misses", "maxsize", "currsize"]) |
| |
| class _HashedSeq(list): |
| __slots__ = 'hashvalue' |
| |
| def __init__(self, tup, hash=hash): |
| self[:] = tup |
| self.hashvalue = hash(tup) |
| |
| def __hash__(self): |
| return self.hashvalue |
| |
| def _make_key(args, kwds, typed, |
| kwd_mark = (object(),), |
| fasttypes = {int, str, frozenset, type(None)}, |
| sorted=sorted, tuple=tuple, type=type, len=len): |
| 'Make a cache key from optionally typed positional and keyword arguments' |
| 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) |
| elif len(key) == 1 and type(key[0]) in fasttypes: |
| return key[0] |
| return _HashedSeq(key) |
| |
| def lru_cache(maxsize=128, 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(). |
| 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). |
| |
| # Constants shared by all lru cache instances: |
| sentinel = object() # unique object used to signal cache misses |
| make_key = _make_key # build a key from the function arguments |
| PREV, NEXT, KEY, RESULT = 0, 1, 2, 3 # names for the link fields |
| |
| def decorating_function(user_function): |
| |
| cache = {} |
| hits = misses = currsize = 0 |
| full = False |
| cache_get = cache.get # bound method to lookup a key or return None |
| 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 |
| |
| 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: |
| |
| def wrapper(*args, **kwds): |
| # simple caching without ordering or size limit |
| nonlocal hits, misses, currsize |
| key = make_key(args, kwds, typed) |
| result = cache_get(key, sentinel) |
| if result is not sentinel: |
| hits += 1 |
| return result |
| result = user_function(*args, **kwds) |
| cache[key] = result |
| misses += 1 |
| currsize += 1 |
| return result |
| |
| else: |
| |
| def wrapper(*args, **kwds): |
| # size limited caching that tracks accesses by recency |
| nonlocal root, hits, misses, currsize, full |
| key = make_key(args, kwds, typed) |
| with lock: |
| 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 |
| result = user_function(*args, **kwds) |
| with lock: |
| if key in cache: |
| # getting here means that this same key was added to the |
| # cache while the lock was released. since the link |
| # update is already done, we need only return the |
| # computed result and update the count of misses. |
| pass |
| elif full: |
| # 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 |
| else: |
| # 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 |
| currsize += 1 |
| full = (currsize == maxsize) |
| misses += 1 |
| return result |
| |
| def cache_info(): |
| """Report cache statistics""" |
| with lock: |
| return _CacheInfo(hits, misses, maxsize, currsize) |
| |
| def cache_clear(): |
| """Clear the cache and cache statistics""" |
| nonlocal hits, misses, currsize, full |
| with lock: |
| cache.clear() |
| root[:] = [root, root, None, None] |
| hits = misses = currsize = 0 |
| full = False |
| |
| wrapper.cache_info = cache_info |
| wrapper.cache_clear = cache_clear |
| return update_wrapper(wrapper, user_function) |
| |
| return decorating_function |