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| """Tree objects that support the `with` statement. | |
| A bit of an OOP mess though. | |
| """ | |
| import contextvars | |
| defaultParent = contextvars.ContextVar('defaultParent', default=None) | |
| treeSessionStack=[] | |
| from collections import UserList | |
| import weakref | |
| class TreeNode: | |
| def __init__(self,parent=None): | |
| if parent != None: | |
| self.parent=parent | |
| elif defaultParent: | |
| self.parent=defaultParent.get() | |
| else: | |
| self.parent=None | |
| super().__init__() | |
| @property | |
| def parent(self): | |
| return self._parent | |
| @parent.setter | |
| def parent(self,obj): | |
| self._reparent(obj,append=True) | |
| def _reparent(self,obj,append=True): | |
| """This bit of code is responsible for ensuring that TreeNodes have 1, and only 1, | |
| parent object. | |
| """ | |
| #ToDo, the control flow on this is awful and dumb. Fix it. | |
| #Need to handle oldParent cleanup at the end or else the object de-references itself and | |
| # gets garbage collected... Or at least I think that's what's going on. | |
| oldParent=getattr(self,"_parent",None) | |
| # Make sure object is a supported type | |
| try: assert isinstance(obj,TreeContainer) or obj == None | |
| except: | |
| raise ValueError(f"Leaf nodes can only have TreeContainers as their parent objects, not {type(obj)}'s like {obj}") | |
| #Add object to new container and set backreference | |
| if append and obj != None: | |
| obj.append(self) | |
| if obj != None: | |
| #We use weakref to avoid reference loops | |
| self._parent = weakref.proxy(obj) | |
| else: | |
| self._parent = None | |
| #Remove item from old container | |
| if oldParent: | |
| while self in oldParent: | |
| oldParent.remove(self) | |
| import contextlib | |
| class TreeContainer(TreeNode,UserList): | |
| def __init__(self,data=list(),*args,**kwargs): | |
| super().__init__(*args,**kwargs) | |
| self.data.extend(data) | |
| self._session_token=None | |
| @contextlib.contextmanager | |
| def __call__(self): | |
| #This version is re-entrant, but needs to be called explicitly... | |
| # that could probably be hacked around, but it would be even more ugly. | |
| session_token=defaultParent.set(self) | |
| yield self | |
| defaultParent.reset(session_token) | |
| def append(self, value): | |
| super().append(value) | |
| try: assert isinstance(value,TreeNode) | |
| except: raise ValueError("TreeContainers can only contain TreeNodes") | |
| value._reparent(self,append=False) | |
| t = TreeContainer() | |
| with t(): | |
| t2 = TreeContainer(['t2',],) | |
| TreeContainer(['t2-sub',],parent=t2) | |
| t3 = TreeContainer(['t3',],) | |
| with t3(): | |
| TreeContainer(['t3-sub',],) | |
| t4 = TreeContainer(['t4',],) | |
| t4.append(TreeContainer(['t4-sub',],)) | |
| t5 = TreeContainer(['t5',],) | |
| tTemp = TreeContainer(['t5-sub',],) | |
| tTemp.parent=t5 | |
| print(t) | |
| #It's almost a test case! | |
| assert repr(t) == "[['t2', ['t2-sub']], ['t3', ['t3-sub']], ['t4', ['t4-sub']], ['t5', ['t5-sub']]]" |
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