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"""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']
from _functools import partial, reduce
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() 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)
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
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
_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().
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):
cache = dict()
hits = misses = 0
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):
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 is None:
@wraps(user_function)
def wrapper(*args, **kwds):
# simple caching without ordering or size limit
nonlocal hits, misses
key = make_key(args, kwds, typed) if kwds or typed else args
result = cache_get(key, root) # root used here as a unique not-found sentinel
if result is not root:
hits += 1
return result
result = user_function(*args, **kwds)
cache[key] = result
misses += 1
return result
else:
@wraps(user_function)
def wrapper(*args, **kwds):
# size limited caching that tracks accesses by recency
nonlocal hits, misses
key = make_key(args, kwds, typed) if kwds or typed else args
with lock:
link = cache_get(key)
if link is not None:
# record recent use of the key by moving it to the front of the list
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:
last = root[PREV]
link = [last, root, key, result]
cache[key] = last[NEXT] = root[PREV] = link
if _len(cache) > maxsize:
# purge least recently used cache entry
old_prev, old_next, old_key, old_result = root[NEXT]
root[NEXT] = old_next
old_next[PREV] = root
del cache[old_key]
misses += 1
return result
def cache_info():
"""Report cache statistics"""
with lock:
return _CacheInfo(hits, misses, maxsize, len(cache))
def cache_clear():
"""Clear the cache and cache statistics"""
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 decorating_function
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