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📛 NAME

graphlib

🚀 Quick Reference

Use Case	Command	Description
🔧 Create a sorter	ts = TopologicalSorter()	Initialize with optional graph dict
➕ Add node with dependencies	ts.add(node, dep1, dep2)	Both node and predecessors must be hashable
✅ Prepare graph	ts.prepare()	Finalize; raises CycleError if cycles exist
📋 Get ready nodes	ts.get_ready()	Returns tuple of nodes with no unresolved predecessors
✔️ Mark done	ts.done(node)	Unblocks successors of processed nodes
🔄 Static order (no prepare/done)	list(ts.static_order())	Iterable of nodes in topological order; raises CycleError
🔍 Check progress	ts.is_active()	Returns True if more nodes can be processed
⚠️ Catch cycle error	try: ... except CycleError as e: ...	Access cycle via e.args[1]

📚 MODULE REFERENCE

https://docs.python.org/3.10/library/graphlib.html

The following documentation is automatically generated from the Python source files. It may be incomplete, incorrect or include features that are considered implementation detail and may vary between Python implementations. When in doubt, consult the module reference at the location listed above.

🏛️ CLASSES

builtins.ValueError(builtins.Exception) → CycleError
builtins.object → TopologicalSorter

⚠️ class CycleError(builtins.ValueError)

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.

Method resolution order: CycleError → builtins.ValueError → builtins.Exception → builtins.BaseException → builtins.object

Data descriptors defined here:

• __weakref__ — list of weak references to the object (if defined)

Methods inherited from builtins.ValueError:

• __init__(self, /, *args, **kwargs) — Initialize self. See help(type(self)) for accurate signature.
• __new__(*args, **kwargs) (static) — Create and return a new object. See help(type) for accurate signature.

Methods inherited from builtins.BaseException:

• __delattr__(self, name, /) — Implement delattr(self, name).
• __getattribute__(self, name, /) — Return getattr(self, name).
• __reduce__(...) — Helper for pickle.
• __repr__(self, /) — Return repr(self).
• __setattr__(self, name, value, /) — Implement setattr(self, name, value).
• __setstate__(...)
• __str__(self, /) — Return str(self).
• with_traceback(...) — Exception.with_traceback(tb) — set self.__traceback__ to tb and return self.

Data descriptors inherited from builtins.BaseException:

• __cause__ — exception cause
• __context__ — exception context
• __dict__
• __suppress_context__
• __traceback__
• args

🔀 class TopologicalSorter(builtins.object)

TopologicalSorter(graph=None)

Provides functionality to topologically sort a graph of hashable nodes.

Methods defined here:

• __bool__(self)
• __init__(self, graph=None) — Initialize self. See help(type(self)) for accurate signature.
• 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 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, CycleError will be raised.

Data descriptors defined here:

• __dict__ — dictionary for instance variables (if defined)
• __weakref__ — list of weak references to the object (if defined)

📦 DATA

__all__ = ['TopologicalSorter', 'CycleError']

📁 FILE

/usr/lib/python3.10/graphlib.py

📛 NAME 🚀 Quick Reference 📚 MODULE REFERENCE 🏛️ CLASSES 📦 DATA 📁 FILE