diff options
Diffstat (limited to 'Lib/functools.py')
| -rw-r--r-- | Lib/functools.py | 245 |
1 files changed, 0 insertions, 245 deletions
diff --git a/Lib/functools.py b/Lib/functools.py index 87c7d87..5cab497 100644 --- a/Lib/functools.py +++ b/Lib/functools.py @@ -11,7 +11,6 @@ __all__ = ['update_wrapper', 'wraps', 'WRAPPER_ASSIGNMENTS', 'WRAPPER_UPDATES', 'total_ordering', 'cache', 'cmp_to_key', 'lru_cache', 'reduce', - 'TopologicalSorter', 'CycleError', 'partial', 'partialmethod', 'singledispatch', 'singledispatchmethod', 'cached_property'] @@ -199,250 +198,6 @@ def total_ordering(cls): setattr(cls, opname, opfunc) return cls -################################################################################ -### topological sort -################################################################################ - -_NODE_OUT = -1 -_NODE_DONE = -2 - - -class _NodeInfo: - __slots__ = 'node', 'npredecessors', 'successors' - - def __init__(self, node): - # The node this class is augmenting. - self.node = node - - # Number of predecessors, generally >= 0. When this value falls to 0, - # and is returned by get_ready(), this is set to _NODE_OUT and when the - # node is marked done by a call to done(), set to _NODE_DONE. - self.npredecessors = 0 - - # List of successor nodes. The list can contain duplicated elements as - # long as they're all reflected in the successor's npredecessors attribute). - self.successors = [] - - -class CycleError(ValueError): - """Subclass of ValueError raised by TopologicalSorterif cycles exist in the graph - - If multiple cycles exist, only one undefined choice among them will be reported - and included in the exception. The detected cycle can be accessed via the second - element in the *args* attribute of the exception instance and consists in a list - of nodes, such that each node is, in the graph, an immediate predecessor of the - next node in the list. In the reported list, the first and the last node will be - the same, to make it clear that it is cyclic. - """ - pass - - -class TopologicalSorter: - """Provides functionality to topologically sort a graph of hashable nodes""" - - def __init__(self, graph=None): - self._node2info = {} - self._ready_nodes = None - self._npassedout = 0 - self._nfinished = 0 - - if graph is not None: - for node, predecessors in graph.items(): - self.add(node, *predecessors) - - def _get_nodeinfo(self, node): - if (result := self._node2info.get(node)) is None: - self._node2info[node] = result = _NodeInfo(node) - return result - - def add(self, node, *predecessors): - """Add a new node and its predecessors to the graph. - - Both the *node* and all elements in *predecessors* must be hashable. - - If called multiple times with the same node argument, the set of dependencies - will be the union of all dependencies passed in. - - It is possible to add a node with no dependencies (*predecessors* is not provided) - as well as provide a dependency twice. If a node that has not been provided before - is included among *predecessors* it will be automatically added to the graph with - no predecessors of its own. - - Raises ValueError if called after "prepare". - """ - if self._ready_nodes is not None: - raise ValueError("Nodes cannot be added after a call to prepare()") - - # Create the node -> predecessor edges - nodeinfo = self._get_nodeinfo(node) - nodeinfo.npredecessors += len(predecessors) - - # Create the predecessor -> node edges - for pred in predecessors: - pred_info = self._get_nodeinfo(pred) - pred_info.successors.append(node) - - def prepare(self): - """Mark the graph as finished and check for cycles in the graph. - - If any cycle is detected, "CycleError" will be raised, but "get_ready" can - still be used to obtain as many nodes as possible until cycles block more - progress. After a call to this function, the graph cannot be modified and - therefore no more nodes can be added using "add". - """ - if self._ready_nodes is not None: - raise ValueError("cannot prepare() more than once") - - self._ready_nodes = [i.node for i in self._node2info.values() - if i.npredecessors == 0] - # ready_nodes is set before we look for cycles on purpose: - # if the user wants to catch the CycleError, that's fine, - # they can continue using the instance to grab as many - # nodes as possible before cycles block more progress - cycle = self._find_cycle() - if cycle: - raise CycleError(f"nodes are in a cycle", cycle) - - def get_ready(self): - """Return a tuple of all the nodes that are ready. - - Initially it returns all nodes with no predecessors; once those are marked - as processed by calling "done", further calls will return all new nodes that - have all their predecessors already processed. Once no more progress can be made, - empty tuples are returned. - - Raises ValueError if called without calling "prepare" previously. - """ - if self._ready_nodes is None: - raise ValueError("prepare() must be called first") - - # Get the nodes that are ready and mark them - result = tuple(self._ready_nodes) - n2i = self._node2info - for node in result: - n2i[node].npredecessors = _NODE_OUT - - # Clean the list of nodes that are ready and update - # the counter of nodes that we have returned. - self._ready_nodes.clear() - self._npassedout += len(result) - - return result - - def is_active(self): - """Return True if more progress can be made and ``False`` otherwise. - - Progress can be made if cycles do not block the resolution and either there - are still nodes ready that haven't yet been returned by "get_ready" or the - number of nodes marked "done" is less than the number that have been returned - by "get_ready". - - Raises ValueError if called without calling "prepare" previously. - """ - if self._ready_nodes is None: - raise ValueError("prepare() must be called first") - return self._nfinished < self._npassedout or bool(self._ready_nodes) - - def __bool__(self): - return self.is_active() - - def done(self, *nodes): - """Marks a set of nodes returned by "get_ready" as processed. - - This method unblocks any successor of each node in *nodes* for being returned - in the future by a a call to "get_ready" - - Raises :exec:`ValueError` if any node in *nodes* has already been marked as - processed by a previous call to this method, if a node was not added to the - graph by using "add" or if called without calling "prepare" previously or if - node has not yet been returned by "get_ready". - """ - - if self._ready_nodes is None: - raise ValueError("prepare() must be called first") - - n2i = self._node2info - - for node in nodes: - - # Check if we know about this node (it was added previously using add() - if (nodeinfo := n2i.get(node)) is None: - raise ValueError(f"node {node!r} was not added using add()") - - # If the node has not being returned (marked as ready) previously, inform the user. - stat = nodeinfo.npredecessors - if stat != _NODE_OUT: - if stat >= 0: - raise ValueError(f"node {node!r} was not passed out (still not ready)") - elif stat == _NODE_DONE: - raise ValueError(f"node {node!r} was already marked done") - else: - assert False, f"node {node!r}: unknown status {stat}" - - # Mark the node as processed - nodeinfo.npredecessors = _NODE_DONE - - # Go to all the successors and reduce the number of predecessors, collecting all the ones - # that are ready to be returned in the next get_ready() call. - for successor in nodeinfo.successors: - successor_info = n2i[successor] - successor_info.npredecessors -= 1 - if successor_info.npredecessors == 0: - self._ready_nodes.append(successor) - self._nfinished += 1 - - def _find_cycle(self): - n2i = self._node2info - stack = [] - itstack = [] - seen = set() - node2stacki = {} - - for node in n2i: - if node in seen: - continue - - while True: - if node in seen: - # If we have seen already the node and is in the - # current stack we have found a cycle. - if node in node2stacki: - return stack[node2stacki[node]:] + [node] - # else go on to get next successor - else: - seen.add(node) - itstack.append(iter(n2i[node].successors).__next__) - node2stacki[node] = len(stack) - stack.append(node) - - # Backtrack to the topmost stack entry with - # at least another successor. - while stack: - try: - node = itstack[-1]() - break - except StopIteration: - del node2stacki[stack.pop()] - itstack.pop() - else: - break - return None - - def static_order(self): - """Returns an iterable of nodes in a topological order. - - The particular order that is returned may depend on the specific - order in which the items were inserted in the graph. - - Using this method does not require to call "prepare" or "done". If any - cycle is detected, :exc:`CycleError` will be raised. - """ - self.prepare() - while self.is_active(): - node_group = self.get_ready() - yield from node_group - self.done(*node_group) - ################################################################################ ### cmp_to_key() function converter |