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Note

This documents the development version of NetworkX. Documentation for the current release can be found here.

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Exceptions

Exceptions

Base exceptions and errors for NetworkX.

class NetworkXException

Base class for exceptions in NetworkX.

class NetworkXError

Exception for a serious error in NetworkX

class NetworkXPointlessConcept

Raised when a null graph is provided as input to an algorithm that cannot use it.

The null graph is sometimes considered a pointless concept 1, thus the name of the exception.

References

1

Harary, F. and Read, R. “Is the Null Graph a Pointless Concept?” In Graphs and Combinatorics Conference, George Washington University. New York: Springer-Verlag, 1973.

class NetworkXAlgorithmError

Exception for unexpected termination of algorithms.

class NetworkXUnfeasible

Exception raised by algorithms trying to solve a problem instance that has no feasible solution.

class NetworkXNoPath

Exception for algorithms that should return a path when running on graphs where such a path does not exist.

class NetworkXNoCycle

Exception for algorithms that should return a cycle when running on graphs where such a cycle does not exist.

class NodeNotFound

Exception raised if requested node is not present in the graph

class HasACycle

Raised if a graph has a cycle when an algorithm expects that it will have no cycles.

class NetworkXUnbounded

Exception raised by algorithms trying to solve a maximization or a minimization problem instance that is unbounded.

class NetworkXNotImplemented

Exception raised by algorithms not implemented for a type of graph.

class AmbiguousSolution

Raised if more than one valid solution exists for an intermediary step of an algorithm.

In the face of ambiguity, refuse the temptation to guess. This may occur, for example, when trying to determine the bipartite node sets in a disconnected bipartite graph when computing bipartite matchings.

class ExceededMaxIterations

Raised if a loop iterates too many times without breaking.

This may occur, for example, in an algorithm that computes progressively better approximations to a value but exceeds an iteration bound specified by the user.

class PowerIterationFailedConvergence(num_iterations, *args, **kw)

Raised when the power iteration method fails to converge within a specified iteration limit.

num_iterations is the number of iterations that have been completed when this exception was raised.