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This module has no docstring.
Subclass of ValueError raised by TopologicalSorter.prepare if cycles
exist in the working 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.
with_traceback(...)
Exception.with_traceback(tb) --
set self.__traceback__ to tb and return self.
args = <attribute 'args' of 'BaseException' objects>
Provides functionality to topologically sort a graph of hashable nodes
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".
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 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".
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.
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.
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".
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.