# License for code in this file that was taken from Python 2.5.
# PYTHON SOFTWARE FOUNDATION LICENSE VERSION 2
# --------------------------------------------
#
# 1. This LICENSE AGREEMENT is between the Python Software Foundation
# ("PSF"), and the Individual or Organization ("Licensee") accessing and
# otherwise using this software ("Python") in source or binary form and
# its associated documentation.
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# 2. Subject to the terms and conditions of this License Agreement, PSF
# hereby grants Licensee a nonexclusive, royalty-free, world-wide
# license to reproduce, analyze, test, perform and/or display publicly,
# prepare derivative works, distribute, and otherwise use Python
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# 2001, 2002, 2003, 2004, 2005, 2006, 2007 Python Software Foundation;
# All Rights Reserved" are retained in Python alone or in any derivative
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# Agreement.
def curry(_curried_func, *args, **kwargs):
def _curried(*moreargs, **morekwargs):
return _curried_func(*(args+moreargs), **dict(kwargs, **morekwargs))
return _curried
### Begin from Python 2.5 functools.py ########################################
# Summary of changes made to the Python 2.5 code below:
# * swapped ``partial`` for ``curry`` to maintain backwards-compatibility
# in Django.
# * Wrapped the ``setattr`` call in ``update_wrapper`` with a try-except
# block to make it compatible with Python 2.3, which doesn't allow
# assigning to ``__name__``.
# Copyright (c) 2001, 2002, 2003, 2004, 2005, 2006, 2007 Python Software Foundation.
# All Rights Reserved.
###############################################################################
# update_wrapper() and wraps() are tools to help write
# wrapper functions that can handle naive introspection
WRAPPER_ASSIGNMENTS = ('__module__', '__name__', '__doc__')
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 off the wrapper that
are updated with the corresponding attribute from the wrapped
function (defaults to functools.WRAPPER_UPDATES)
"""
for attr in assigned:
try:
setattr(wrapper, attr, getattr(wrapped, attr))
except TypeError: # Python 2.3 doesn't allow assigning to __name__.
pass
for attr in updated:
getattr(wrapper, attr).update(getattr(wrapped, attr))
# Return the wrapper so this can be used as a decorator via curry()
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 curry() to
update_wrapper().
"""
return curry(update_wrapper, wrapped=wrapped,
assigned=assigned, updated=updated)
### End from Python 2.5 functools.py ##########################################
def memoize(func, cache, num_args):
"""
Wrap a function so that results for any argument tuple are stored in
'cache'. Note that the args to the function must be usable as dictionary
keys.
Only the first num_args are considered when creating the key.
"""
def wrapper(*args):
mem_args = args[:num_args]
if mem_args in cache:
return cache[mem_args]
result = func(*args)
cache[mem_args] = result
return result
return wraps(func)(wrapper)
class Promise(object):
"""
This is just a base class for the proxy class created in
the closure of the lazy function. It can be used to recognize
promises in code.
"""
pass
def lazy(func, *resultclasses):
"""
Turns any callable into a lazy evaluated callable. You need to give result
classes or types -- at least one is needed so that the automatic forcing of
the lazy evaluation code is triggered. Results are not memoized; the
function is evaluated on every access.
"""
class __proxy__(Promise):
"""
Encapsulate a function call and act as a proxy for methods that are
called on the result of that function. The function is not evaluated
until one of the methods on the result is called.
"""
__dispatch = None
def __init__(self, args, kw):
self.__func = func
self.__args = args
self.__kw = kw
if self.__dispatch is None:
self.__prepare_class__()
def __reduce__(self):
return (
_lazy_proxy_unpickle,
(self.__func, self.__args, self.__kw) + resultclasses
)
def __prepare_class__(cls):
cls.__dispatch = {}
for resultclass in resultclasses:
cls.__dispatch[resultclass] = {}
for (k, v) in resultclass.__dict__.items():
# All __promise__ return the same wrapper method, but they
# also do setup, inserting the method into the dispatch
# dict.
meth = cls.__promise__(resultclass, k, v)
if hasattr(cls, k):
continue
setattr(cls, k, meth)
cls._delegate_str = str in resultclasses
cls._delegate_unicode = unicode in resultclasses
assert not (cls._delegate_str and cls._delegate_unicode), "Cannot call lazy() with both str and unicode return types."
if cls._delegate_unicode:
cls.__unicode__ = cls.__unicode_cast
elif cls._delegate_str:
cls.__str__ = cls.__str_cast
__prepare_class__ = classmethod(__prepare_class__)
def __promise__(cls, klass, funcname, func):
# Builds a wrapper around some magic method and registers that magic
# method for the given type and method name.
def __wrapper__(self, *args, **kw):
# Automatically triggers the evaluation of a lazy value and
# applies the given magic method of the result type.
res = self.__func(*self.__args, **self.__kw)
for t in type(res).mro():
if t in self.__dispatch:
return self.__dispatch[t][funcname](res, *args, **kw)
raise TypeError("Lazy object returned unexpected type.")
if klass not in cls.__dispatch:
cls.__dispatch[klass] = {}
cls.__dispatch[klass][funcname] = func
return __wrapper__
__promise__ = classmethod(__promise__)
def __unicode_cast(self):
return self.__func(*self.__args, **self.__kw)
def __str_cast(self):
return str(self.__func(*self.__args, **self.__kw))
def __cmp__(self, rhs):
if self._delegate_str:
s = str(self.__func(*self.__args, **self.__kw))
elif self._delegate_unicode:
s = unicode(self.__func(*self.__args, **self.__kw))
else:
s = self.__func(*self.__args, **self.__kw)
if isinstance(rhs, Promise):
return -cmp(rhs, s)
else:
return cmp(s, rhs)
def __mod__(self, rhs):
if self._delegate_str:
return str(self) % rhs
elif self._delegate_unicode:
return unicode(self) % rhs
else:
raise AssertionError('__mod__ not supported for non-string types')
def __deepcopy__(self, memo):
# Instances of this class are effectively immutable. It's just a
# collection of functions. So we don't need to do anything
# complicated for copying.
memo[id(self)] = self
return self
def __wrapper__(*args, **kw):
# Creates the proxy object, instead of the actual value.
return __proxy__(args, kw)
return wraps(func)(__wrapper__)
def _lazy_proxy_unpickle(func, args, kwargs, *resultclasses):
return lazy(func, *resultclasses)(*args, **kwargs)
def allow_lazy(func, *resultclasses):
"""
A decorator that allows a function to be called with one or more lazy
arguments. If none of the args are lazy, the function is evaluated
immediately, otherwise a __proxy__ is returned that will evaluate the
function when needed.
"""
def wrapper(*args, **kwargs):
for arg in list(args) + kwargs.values():
if isinstance(arg, Promise):
break
else:
return func(*args, **kwargs)
return lazy(func, *resultclasses)(*args, **kwargs)
return wraps(func)(wrapper)
class LazyObject(object):
"""
A wrapper for another class that can be used to delay instantiation of the
wrapped class.
By subclassing, you have the opportunity to intercept and alter the
instantiation. If you don't need to do that, use SimpleLazyObject.
"""
def __init__(self):
self._wrapped = None
def __getattr__(self, name):
if self._wrapped is None:
self._setup()
return getattr(self._wrapped, name)
def __setattr__(self, name, value):
if name == "_wrapped":
# Assign to __dict__ to avoid infinite __setattr__ loops.
self.__dict__["_wrapped"] = value
else:
if self._wrapped is None:
self._setup()
setattr(self._wrapped, name, value)
def __delattr__(self, name):
if name == "_wrapped":
raise TypeError("can't delete _wrapped.")
if self._wrapped is None:
self._setup()
delattr(self._wrapped, name)
def _setup(self):
"""
Must be implemented by subclasses to initialise the wrapped object.
"""
raise NotImplementedError
# introspection support:
__members__ = property(lambda self: self.__dir__())
def __dir__(self):
if self._wrapped is None:
self._setup()
return dir(self._wrapped)
class SimpleLazyObject(LazyObject):
"""
A lazy object initialised from any function.
Designed for compound objects of unknown type. For builtins or objects of
known type, use django.utils.functional.lazy.
"""
def __init__(self, func):
"""
Pass in a callable that returns the object to be wrapped.
If copies are made of the resulting SimpleLazyObject, which can happen
in various circumstances within Django, then you must ensure that the
callable can be safely run more than once and will return the same
value.
"""
self.__dict__['_setupfunc'] = func
# For some reason, we have to inline LazyObject.__init__ here to avoid
# recursion
self._wrapped = None
def __str__(self):
if self._wrapped is None: self._setup()
return str(self._wrapped)
def __unicode__(self):
if self._wrapped is None: self._setup()
return unicode(self._wrapped)
def __deepcopy__(self, memo):
if self._wrapped is None:
# We have to use SimpleLazyObject, not self.__class__, because the
# latter is proxied.
result = SimpleLazyObject(self._setupfunc)
memo[id(self)] = result
return result
else:
# Changed to use deepcopy from copycompat, instead of copy
# For Python 2.4.
from django.utils.copycompat import deepcopy
return deepcopy(self._wrapped, memo)
# Need to pretend to be the wrapped class, for the sake of objects that care
# about this (especially in equality tests)
def __get_class(self):
if self._wrapped is None: self._setup()
return self._wrapped.__class__
__class__ = property(__get_class)
def __eq__(self, other):
if self._wrapped is None: self._setup()
return self._wrapped == other
def __hash__(self):
if self._wrapped is None: self._setup()
return hash(self._wrapped)
def _setup(self):
self._wrapped = self._setupfunc()
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