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# copyright 2003-2013 LOGILAB S.A. (Paris, FRANCE), all rights reserved.
# contact --
# This file is part of logilab-common.
# logilab-common is free software: you can redistribute it and/or modify it under
# the terms of the GNU Lesser General Public License as published by the Free
# Software Foundation, either version 2.1 of the License, or (at your option) any
# later version.
# logilab-common is distributed in the hope that it will be useful, but WITHOUT
# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
# FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
# details.
# You should have received a copy of the GNU Lesser General Public License along
# with logilab-common. If not, see <>.
""" A few useful function/method decorators. """
from __future__ import print_function
__docformat__ = "restructuredtext en"
import sys
import types
from time import clock, time
from inspect import isgeneratorfunction, getargspec
from logilab.common.compat import method_type
# XXX rewrite so we can use the decorator syntax when keyarg has to be specified
class cached_decorator(object):
def __init__(self, cacheattr=None, keyarg=None):
self.cacheattr = cacheattr
self.keyarg = keyarg
def __call__(self, callableobj=None):
assert not isgeneratorfunction(callableobj), \
'cannot cache generator function: %s' % callableobj
if len(getargspec(callableobj).args) == 1 or self.keyarg == 0:
cache = _SingleValueCache(callableobj, self.cacheattr)
elif self.keyarg:
cache = _MultiValuesKeyArgCache(callableobj, self.keyarg, self.cacheattr)
cache = _MultiValuesCache(callableobj, self.cacheattr)
return cache.closure()
class _SingleValueCache(object):
def __init__(self, callableobj, cacheattr=None):
self.callable = callableobj
if cacheattr is None:
self.cacheattr = '_%s_cache_' % callableobj.__name__
assert cacheattr != callableobj.__name__
self.cacheattr = cacheattr
def __call__(__me, self, *args):
return self.__dict__[__me.cacheattr]
except KeyError:
value = __me.callable(self, *args)
setattr(self, __me.cacheattr, value)
return value
def closure(self):
def wrapped(*args, **kwargs):
return self.__call__(*args, **kwargs)
wrapped.cache_obj = self
wrapped.__doc__ = self.callable.__doc__
wrapped.__name__ = self.callable.__name__
return wrapped
def clear(self, holder):
holder.__dict__.pop(self.cacheattr, None)
class _MultiValuesCache(_SingleValueCache):
def _get_cache(self, holder):
_cache = holder.__dict__[self.cacheattr]
except KeyError:
_cache = {}
setattr(holder, self.cacheattr, _cache)
return _cache
def __call__(__me, self, *args, **kwargs):
_cache = __me._get_cache(self)
return _cache[args]
except KeyError:
_cache[args] = __me.callable(self, *args)
return _cache[args]
class _MultiValuesKeyArgCache(_MultiValuesCache):
def __init__(self, callableobj, keyarg, cacheattr=None):
super(_MultiValuesKeyArgCache, self).__init__(callableobj, cacheattr)
self.keyarg = keyarg
def __call__(__me, self, *args, **kwargs):
_cache = __me._get_cache(self)
key = args[__me.keyarg-1]
return _cache[key]
except KeyError:
_cache[key] = __me.callable(self, *args, **kwargs)
return _cache[key]
def cached(callableobj=None, keyarg=None, **kwargs):
"""Simple decorator to cache result of method call."""
kwargs['keyarg'] = keyarg
decorator = cached_decorator(**kwargs)
if callableobj is None:
return decorator
return decorator(callableobj)
class cachedproperty(object):
""" Provides a cached property equivalent to the stacking of
@cached and @property, but more efficient.
After first usage, the <property_name> becomes part of the object's
__dict__. Doing:
del obj.<property_name> empties the cache.
Idea taken from the pyramid_ framework and the mercurial_ project.
.. _pyramid:
.. _mercurial:
__slots__ = ('wrapped',)
def __init__(self, wrapped):
except AttributeError:
raise TypeError('%s must have a __name__ attribute' %
self.wrapped = wrapped
def __doc__(self):
doc = getattr(self.wrapped, '__doc__', None)
return ('<wrapped by the cachedproperty decorator>%s'
% ('\n%s' % doc if doc else ''))
def __get__(self, inst, objtype=None):
if inst is None:
return self
val = self.wrapped(inst)
setattr(inst, self.wrapped.__name__, val)
return val
def get_cache_impl(obj, funcname):
cls = obj.__class__
member = getattr(cls, funcname)
if isinstance(member, property):
member = member.fget
return member.cache_obj
def clear_cache(obj, funcname):
"""Clear a cache handled by the :func:`cached` decorator. If 'x' class has
@cached on its method `foo`, type
>>> clear_cache(x, 'foo')
to purge this method's cache on the instance.
get_cache_impl(obj, funcname).clear(obj)
def copy_cache(obj, funcname, cacheobj):
"""Copy cache for <funcname> from cacheobj to obj."""
cacheattr = get_cache_impl(obj, funcname).cacheattr
setattr(obj, cacheattr, cacheobj.__dict__[cacheattr])
except KeyError:
class wproperty(object):
"""Simple descriptor expecting to take a modifier function as first argument
and looking for a _<function name> to retrieve the attribute.
def __init__(self, setfunc):
self.setfunc = setfunc
self.attrname = '_%s' % setfunc.__name__
def __set__(self, obj, value):
self.setfunc(obj, value)
def __get__(self, obj, cls):
assert obj is not None
return getattr(obj, self.attrname)
class classproperty(object):
"""this is a simple property-like class but for class attributes.
def __init__(self, get):
self.get = get
def __get__(self, inst, cls):
return self.get(cls)
class iclassmethod(object):
'''Descriptor for method which should be available as class method if called
on the class or instance method if called on an instance.
def __init__(self, func):
self.func = func
def __get__(self, instance, objtype):
if instance is None:
return method_type(self.func, objtype, objtype.__class__)
return method_type(self.func, instance, objtype)
def __set__(self, instance, value):
raise AttributeError("can't set attribute")
def timed(f):
def wrap(*args, **kwargs):
t = time()
c = clock()
res = f(*args, **kwargs)
print('%s clock: %.9f / time: %.9f' % (f.__name__,
clock() - c, time() - t))
return res
return wrap
def locked(acquire, release):
"""Decorator taking two methods to acquire/release a lock as argument,
returning a decorator function which will call the inner method after
having called acquire(self) et will call release(self) afterwards.
def decorator(f):
def wrapper(self, *args, **kwargs):
return f(self, *args, **kwargs)
return wrapper
return decorator
def monkeypatch(klass, methodname=None):
"""Decorator extending class with the decorated callable. This is basically
a syntactic sugar vs class assignment.
>>> class A:
... pass
>>> @monkeypatch(A)
... def meth(self):
... return 12
>>> a = A()
>>> a.meth()
>>> @monkeypatch(A, 'foo')
... def meth(self):
... return 12
def decorator(func):
name = methodname or func.__name__
except AttributeError:
raise AttributeError('%s has no __name__ attribute: '
'you should provide an explicit `methodname`'
% func)
setattr(klass, name, func)
return func
return decorator