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Diffstat (limited to 'intern/python/modules/mcf/utils/namespace.py')
| -rw-r--r-- | intern/python/modules/mcf/utils/namespace.py | 224 |
1 files changed, 224 insertions, 0 deletions
diff --git a/intern/python/modules/mcf/utils/namespace.py b/intern/python/modules/mcf/utils/namespace.py new file mode 100644 index 00000000000..819531e10db --- /dev/null +++ b/intern/python/modules/mcf/utils/namespace.py @@ -0,0 +1,224 @@ +''' +NameSpace v0.04: + +A "NameSpace" is an object wrapper around a _base dictionary +which allows chaining searches for an 'attribute' within that +dictionary, or any other namespace which is defined as part +of the search path (depending on the downcascade variable, is +either the hier-parents or the hier-children). + +You can assign attributes to the namespace normally, and read +them normally. (setattr, getattr, a.this = that, a.this) + +I use namespaces for writing parsing systems, where I want to +differentiate between sources (have multiple sources that I can +swap into or out of the namespace), but want to be able to get +at them through a single interface. There is a test function +which gives you an idea how to use the system. + +In general, call NameSpace(someobj), where someobj is a dictionary, +a module, or another NameSpace, and it will return a NameSpace which +wraps up the keys of someobj. To add a namespace to the NameSpace, +just call the append (or hier_addchild) method of the parent namespace +with the child as argument. + +### NOTE: if you pass a module (or anything else with a dict attribute), +names which start with '__' will be removed. You can avoid this by +pre-copying the dict of the object and passing it as the arg to the +__init__ method. + +### NOTE: to properly pickle and/or copy module-based namespaces you +will likely want to do: from mcf.utils import extpkl, copy_extend + +### Changes: + 97.05.04 -- Altered to use standard hierobj interface, cleaned up + interface by removing the "addparent" function, which is reachable + by simply appending to the __parent__ attribute, though normally + you would want to use the hier_addchild or append functions, since + they let both objects know about the addition (and therefor the + relationship will be restored if the objects are stored and unstored) + + 97.06.26 -- Altered the getattr function to reduce the number of + situations in which infinite lookup loops could be created + (unfortunately, the cost is rather high). Made the downcascade + variable harden (resolve) at init, instead of checking for every + lookup. (see next note) + + 97.08.29 -- Discovered some _very_ weird behaviour when storing + namespaces in mcf.store dbases. Resolved it by storing the + __namespace_cascade__ attribute as a normal attribute instead of + using the __unstore__ mechanism... There was really no need to + use the __unstore__, but figuring out how a functions saying + self.__dict__['__namespace_cascade__'] = something + print `self.__dict__['__namespace_cascade__']` can print nothing + is a bit beyond me. (without causing an exception, mind you) + + 97.11.15 Found yet more errors, decided to make two different + classes of namespace. Those based on modules now act similar + to dummy objects, that is, they let you modify the original + instead of keeping a copy of the original and modifying that. + + 98.03.15 -- Eliminated custom pickling methods as they are no longer + needed for use with Python 1.5final + + 98.03.15 -- Fixed bug in items, values, etceteras with module-type + base objects. +''' +import copy, types, string +import hierobj + +class NameSpace(hierobj.Hierobj): + ''' + An hierarchic NameSpace, allows specification of upward or downward + chaining search for resolving names + ''' + def __init__(self, val = None, parents=None, downcascade=1,children=[]): + ''' + A NameSpace can be initialised with a dictionary, a dummied + dictionary, another namespace, or something which has a __dict__ + attribute. + Note that downcascade is hardened (resolved) at init, not at + lookup time. + ''' + hierobj.Hierobj.__init__(self, parents, children) + self.__dict__['__downcascade__'] = downcascade # boolean + if val is None: + self.__dict__['_base'] = {} + else: + if type( val ) == types.StringType: + # this is a reference to a module which has been pickled + val = __import__( val, {},{}, string.split( val, '.') ) + try: + # See if val's a dummy-style object which has a _base + self.__dict__['_base']=copy.copy(val._base) + except (AttributeError,KeyError): + # not a dummy-style object... see if it has a dict attribute... + try: + if type(val) != types.ModuleType: + val = copy.copy(val.__dict__) + except (AttributeError, KeyError): + pass + # whatever val is now, it's going to become our _base... + self.__dict__['_base']=val + # harden (resolve) the reference to downcascade to speed attribute lookups + if downcascade: self.__dict__['__namespace_cascade__'] = self.__childlist__ + else: self.__dict__['__namespace_cascade__'] = self.__parent__ + def __setattr__(self, var, val): + ''' + An attempt to set an attribute should place the attribute in the _base + dictionary through a setitem call. + ''' + # Note that we use standard attribute access to allow ObStore loading if the + # ._base isn't yet available. + try: + self._base[var] = val + except TypeError: + setattr(self._base, var, val) + def __getattr__(self,var): +## print '__getattr__', var + return self.__safe_getattr__(var, {}) # the {} is a stopdict + + def __safe_getattr__(self, var,stopdict): + ''' + We have a lot to do in this function, if the attribute is an unloaded + but stored attribute, we need to load it. If it's not in the stored + attributes, then we need to load the _base, then see if it's in the + _base. + If it's not found by then, then we need to check our resource namespaces + and see if it's in them. + ''' + # we don't have a __storedattr__ or it doesn't have this key... + if var != '_base': + try: + return self._base[var] + except (KeyError,TypeError), x: + try: + return getattr(self._base, var) + except AttributeError: + pass + try: # with pickle, it tries to get the __setstate__ before restoration is complete + for cas in self.__dict__['__namespace_cascade__']: + try: + stopdict[id(cas)] # if succeeds, we've already tried this child + # no need to do anything, if none of the children succeeds we will + # raise an AttributeError + except KeyError: + stopdict[id(cas)] = None + return cas.__safe_getattr__(var,stopdict) + except (KeyError,AttributeError): + pass + raise AttributeError, var + def items(self): + try: + return self._base.items() + except AttributeError: + pass + try: + return self._base.__dict__.items() + except AttributeError: + pass + def keys(self): + try: + return self._base.keys() + except AttributeError: + pass + try: + return self._base.__dict__.keys() + except AttributeError: + pass + def has_key( self, key ): + try: + return self._base.has_key( key) + except AttributeError: + pass + try: + return self._base.__dict__.has_key( key) + except AttributeError: + pass + def values(self): + try: + return self._base.values() + except AttributeError: + pass + try: + return self._base.__dict__.values() + except AttributeError: + pass + + def __getinitargs__(self): + if type( self._base ) is types.ModuleType: + base = self._base.__name__ + else: + base = self._base + return (base, self.__parent__, self.__downcascade__, self.__childlist__) + def __getstate__(self): + return None + def __setstate__(self,*args): + pass + def __deepcopy__(self, memo=None): + d = id(self) + if memo is None: + memo = {} + elif memo.has_key(d): + return memo[d] + if type(self._base) == types.ModuleType: + rest = tuple(map( copy.deepcopy, (self.__parent__, self.__downcascade__, self.__childlist__) )) + new = apply(self.__class__, (self._base,)+rest ) + else: + new = tuple(map( copy.deepcopy, (self._base, self.__parent__, self.__downcascade__, self.__childlist__) )) + return new +## def __del__( self, id=id ): +## print 'del namespace', id( self ) + + +def test(): + import string + a = NameSpace(string) + del(string) + a.append(NameSpace({'a':23,'b':42})) + import math + a.append(NameSpace(math)) + print 'The returned object should allow access to the attributes of the string,\nand math modules, and two simple variables "a" and "b" (== 23 and42 respectively)' + return a + + |