/usr/lib/python2.7/dist-packages/celery/utils/functional.py is in python-celery 3.1.20-1.
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"""
celery.utils.functional
~~~~~~~~~~~~~~~~~~~~~~~
Utilities for functions.
"""
from __future__ import absolute_import
import sys
import threading
from functools import wraps
from itertools import islice
from kombu.utils import cached_property
from kombu.utils.functional import lazy, maybe_evaluate, is_list, maybe_list
from kombu.utils.compat import OrderedDict
from celery.five import UserDict, UserList, items, keys, range
__all__ = ['LRUCache', 'is_list', 'maybe_list', 'memoize', 'mlazy', 'noop',
'first', 'firstmethod', 'chunks', 'padlist', 'mattrgetter', 'uniq',
'regen', 'dictfilter', 'lazy', 'maybe_evaluate']
IS_PY3 = sys.version_info[0] == 3
KEYWORD_MARK = object()
class DummyContext(object):
def __enter__(self):
return self
def __exit__(self, *exc_info):
pass
class LRUCache(UserDict):
"""LRU Cache implementation using a doubly linked list to track access.
:keyword limit: The maximum number of keys to keep in the cache.
When a new key is inserted and the limit has been exceeded,
the *Least Recently Used* key will be discarded from the
cache.
"""
def __init__(self, limit=None):
self.limit = limit
self.mutex = threading.RLock()
self.data = OrderedDict()
def __getitem__(self, key):
with self.mutex:
value = self[key] = self.data.pop(key)
return value
def update(self, *args, **kwargs):
with self.mutex:
data, limit = self.data, self.limit
data.update(*args, **kwargs)
if limit and len(data) > limit:
# pop additional items in case limit exceeded
for _ in range(len(data) - limit):
data.popitem(last=False)
def popitem(self, last=True):
with self.mutex:
return self.data.popitem(last)
def __setitem__(self, key, value):
# remove least recently used key.
with self.mutex:
if self.limit and len(self.data) >= self.limit:
self.data.pop(next(iter(self.data)))
self.data[key] = value
def __iter__(self):
return iter(self.data)
def _iterate_items(self):
with self.mutex:
for k in self:
try:
yield (k, self.data[k])
except KeyError: # pragma: no cover
pass
iteritems = _iterate_items
def _iterate_values(self):
with self.mutex:
for k in self:
try:
yield self.data[k]
except KeyError: # pragma: no cover
pass
itervalues = _iterate_values
def _iterate_keys(self):
# userdict.keys in py3k calls __getitem__
with self.mutex:
return keys(self.data)
iterkeys = _iterate_keys
def incr(self, key, delta=1):
with self.mutex:
# this acts as memcached does- store as a string, but return a
# integer as long as it exists and we can cast it
newval = int(self.data.pop(key)) + delta
self[key] = str(newval)
return newval
def __getstate__(self):
d = dict(vars(self))
d.pop('mutex')
return d
def __setstate__(self, state):
self.__dict__ = state
self.mutex = threading.RLock()
if sys.version_info[0] == 3: # pragma: no cover
keys = _iterate_keys
values = _iterate_values
items = _iterate_items
else: # noqa
def keys(self):
return list(self._iterate_keys())
def values(self):
return list(self._iterate_values())
def items(self):
return list(self._iterate_items())
def memoize(maxsize=None, keyfun=None, Cache=LRUCache):
def _memoize(fun):
mutex = threading.Lock()
cache = Cache(limit=maxsize)
@wraps(fun)
def _M(*args, **kwargs):
if keyfun:
key = keyfun(args, kwargs)
else:
key = args + (KEYWORD_MARK, ) + tuple(sorted(kwargs.items()))
try:
with mutex:
value = cache[key]
except KeyError:
value = fun(*args, **kwargs)
_M.misses += 1
with mutex:
cache[key] = value
else:
_M.hits += 1
return value
def clear():
"""Clear the cache and reset cache statistics."""
cache.clear()
_M.hits = _M.misses = 0
_M.hits = _M.misses = 0
_M.clear = clear
_M.original_func = fun
return _M
return _memoize
class mlazy(lazy):
"""Memoized lazy evaluation.
The function is only evaluated once, every subsequent access
will return the same value.
.. attribute:: evaluated
Set to to :const:`True` after the object has been evaluated.
"""
evaluated = False
_value = None
def evaluate(self):
if not self.evaluated:
self._value = super(mlazy, self).evaluate()
self.evaluated = True
return self._value
def noop(*args, **kwargs):
"""No operation.
Takes any arguments/keyword arguments and does nothing.
"""
pass
def first(predicate, it):
"""Return the first element in `iterable` that `predicate` Gives a
:const:`True` value for.
If `predicate` is None it will return the first item that is not None.
"""
return next(
(v for v in it if (predicate(v) if predicate else v is not None)),
None,
)
def firstmethod(method):
"""Return a function that with a list of instances,
finds the first instance that gives a value for the given method.
The list can also contain lazy instances
(:class:`~kombu.utils.functional.lazy`.)
"""
def _matcher(it, *args, **kwargs):
for obj in it:
try:
answer = getattr(maybe_evaluate(obj), method)(*args, **kwargs)
except AttributeError:
pass
else:
if answer is not None:
return answer
return _matcher
def chunks(it, n):
"""Split an iterator into chunks with `n` elements each.
Examples
# n == 2
>>> x = chunks(iter([0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]), 2)
>>> list(x)
[[0, 1], [2, 3], [4, 5], [6, 7], [8, 9], [10]]
# n == 3
>>> x = chunks(iter([0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]), 3)
>>> list(x)
[[0, 1, 2], [3, 4, 5], [6, 7, 8], [9, 10]]
"""
# XXX This function is not used anymore, at least not by Celery itself.
for first in it:
yield [first] + list(islice(it, n - 1))
def padlist(container, size, default=None):
"""Pad list with default elements.
Examples:
>>> first, last, city = padlist(['George', 'Costanza', 'NYC'], 3)
('George', 'Costanza', 'NYC')
>>> first, last, city = padlist(['George', 'Costanza'], 3)
('George', 'Costanza', None)
>>> first, last, city, planet = padlist(
... ['George', 'Costanza', 'NYC'], 4, default='Earth',
... )
('George', 'Costanza', 'NYC', 'Earth')
"""
return list(container)[:size] + [default] * (size - len(container))
def mattrgetter(*attrs):
"""Like :func:`operator.itemgetter` but return :const:`None` on missing
attributes instead of raising :exc:`AttributeError`."""
return lambda obj: dict((attr, getattr(obj, attr, None))
for attr in attrs)
def uniq(it):
"""Return all unique elements in ``it``, preserving order."""
seen = set()
return (seen.add(obj) or obj for obj in it if obj not in seen)
def regen(it):
"""Regen takes any iterable, and if the object is an
generator it will cache the evaluated list on first access,
so that the generator can be "consumed" multiple times."""
if isinstance(it, (list, tuple)):
return it
return _regen(it)
class _regen(UserList, list):
# must be subclass of list so that json can encode.
def __init__(self, it):
self.__it = it
def __reduce__(self):
return list, (self.data, )
def __length_hint__(self):
return self.__it.__length_hint__()
@cached_property
def data(self):
return list(self.__it)
def dictfilter(d=None, **kw):
"""Remove all keys from dict ``d`` whose value is :const:`None`"""
d = kw if d is None else (dict(d, **kw) if kw else d)
return dict((k, v) for k, v in items(d) if v is not None)
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