'''

altgraph - a python graph library
=================================

altgraph is a fork of graphlib U{http://pygraphlib.sourceforge.net} tailored
to use newer Python 2.3+ features, including additional support used by the
py2app suite (modulegraph and macholib, specifically).

altgraph is a python based graph (network) representation and manipulation package.
It has started out as an extension to the C{graph_lib} module written by Nathan Denny
U{http://www.ece.arizona.edu/~denny/python_nest/graph_lib_1.0.1.html} but over time
it has been significantly optimized and expanded.

The L{Graph} class is loosely modeled after the U{LEDA<http://www.algorithmic-solutions.com/enleda.htm>} (Library of Efficient Datatypes)  representation. The library
includes methods for constructing graphs, BFS and DFS traversals,
topological sort, finding connected components, shortest paths as well as a number
graph statistics functions. The library can also visualize graphs
via U{graphviz<http://www.research.att.com/sw/tools/graphviz/>}.

The package contains the following modules:
    -  the L{Graph} module contains the L{Graph.Graph} class that stores the graph data
    -  the L{GraphAlgo} implements graph algorithms operating on graphs (L{Graph.Graph} instances)
    -  the L{GraphStat} contains functions for computing statistical measures on graphs
    -  the L{GraphUtil} contains functions for generating, reading and saving graphs
    -  the L{Dot}  contains functions for displaying graphs via U{graphviz<http://www.research.att.com/sw/tools/graphviz/>}.

Download
--------

Download the  U{python source code<../dist>}.

Installation
------------

Download and unpack the archive then type::

    python setup.py install

This will install the library in the default location. For instructions on
how to customize the install procedure read the output of::

    python setup.py --help install

To verify the installation procedure switch to the test directory and run the
test_graphib.py file that is located there::

    python test_altgraph.py

Example usage
-------------

Lets assume that we want to analyze the graph below (links to the full picture) GRAPH_IMG.
Our script then might look the following way::

    from altgraph import Graph, GraphAlgo, Dot

    # these are the edges
    edges = [ (1,2), (2,4), (1,3), (2,4), (3,4), (4,5), (6,5),
    (6,14), (14,15), (6, 15),  (5,7), (7, 8), (7,13), (12,8),
    (8,13), (11,12), (11,9), (13,11), (9,13), (13,10) ]

    # creates the graph
    graph = Graph.Graph()
    for head, tail in edges:
        graph.add_edge(head, tail)

    # do a forward bfs from 1 at most to 20
    print graph.forw_bfs(1)

This will print the nodes in some breadth first order::

    [1, 2, 3, 4, 5, 7, 8, 13, 11, 10, 12, 9]

If we wanted to get the hop-distance from node 1 to node 8
we coud write::

    print graph.get_hops(1, 8)

This will print the following::

    [(1, 0), (2, 1), (3, 1), (4, 2), (5, 3), (7, 4), (8, 5)]

Node 1 is at 0 hops since it is the starting node, nodes 2,3 are 1 hop away ...
node 8 is 5 hops away. To find the shortest distance between two nodes you
can use::

    print GraphAlgo.shortest_path(graph, 1, 12)

It will print the nodes on one (if there are more) the shortest paths::

    [1, 2, 4, 5, 7, 13, 11, 12]

To display the graph we can use the GraphViz backend::

    dot = Dot.Dot(graph)

    # display the graph on the monitor
    dot.display()

    # save it in an image file
    dot.save_img(file_name='graph', file_type='gif')


@author: U{Istvan Albert<http://www.personal.psu.edu/staff/i/u/iua1/>}

@license:  MIT License

Copyright (c) 2004 Istvan Albert unless otherwise noted.

Permission is hereby granted, free of charge, to any person obtaining a copy of this software
and associated documentation files (the "Software"), to deal in the Software without restriction,
including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense,
and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do
so.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE
FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
@requires: Python 2.3 or higher

@newfield contributor: Contributors:
@contributor: U{Reka Albert <http://www.phys.psu.edu/~ralbert/>}

'''

__version__ = '0.6.7'

class GraphError(ValueError):
    pass