NetworkX

Source code for networkx.readwrite.nx_shp

"""
*********
Shapefile
*********

Generates a networkx.DiGraph from point and line shapefiles.

"The Esri Shapefile or simply a shapefile is a popular geospatial vector
data format for geographic information systems software. It is developed
and regulated by Esri as a (mostly) open specification for data
interoperability among Esri and other software products."
See http://en.wikipedia.org/wiki/Shapefile for additional information.
"""
#    Copyright (C) 2004-2010 by
#    Ben Reilly <benwreilly@gmail.com>
#    Aric Hagberg <hagberg@lanl.gov>
#    Dan Schult <dschult@colgate.edu>
#    Pieter Swart <swart@lanl.gov>
#    All rights reserved.
#    BSD license.
import networkx as nx
__author__ = """Ben Reilly (benwreilly@gmail.com)"""
__all__ = ['read_shp', 'write_shp']


[docs]def read_shp(path): """Generates a networkx.DiGraph from shapefiles. Point geometries are translated into nodes, lines into edges. Coordinate tuples are used as keys. Attributes are preserved, line geometries are simplified into start and end coordinates. Accepts a single shapefile or directory of many shapefiles. "The Esri Shapefile or simply a shapefile is a popular geospatial vector data format for geographic information systems software [1]_." Parameters ---------- path : file or string File, directory, or filename to read. Returns ------- G : NetworkX graph Examples -------- >>> G=nx.read_shp('test.shp') # doctest: +SKIP References ---------- .. [1] http://en.wikipedia.org/wiki/Shapefile """ try: from osgeo import ogr except ImportError: raise ImportError("read_shp requires OGR: http://www.gdal.org/") net = nx.DiGraph() def getfieldinfo(lyr, feature, flds): f = feature return [f.GetField(f.GetFieldIndex(x)) for x in flds] def addlyr(lyr, fields): for findex in xrange(lyr.GetFeatureCount()): f = lyr.GetFeature(findex) flddata = getfieldinfo(lyr, f, fields) g = f.geometry() attributes = dict(zip(fields, flddata)) attributes["ShpName"] = lyr.GetName() if g.GetGeometryType() == 1: # point net.add_node((g.GetPoint_2D(0)), attributes) if g.GetGeometryType() == 2: # linestring attributes["Wkb"] = g.ExportToWkb() attributes["Wkt"] = g.ExportToWkt() attributes["Json"] = g.ExportToJson() last = g.GetPointCount() - 1 net.add_edge(g.GetPoint_2D(0), g.GetPoint_2D(last), attributes) if isinstance(path, str): shp = ogr.Open(path) lyrcount = shp.GetLayerCount() # multiple layers indicate a directory for lyrindex in xrange(lyrcount): lyr = shp.GetLayerByIndex(lyrindex) flds = [x.GetName() for x in lyr.schema] addlyr(lyr, flds) return net
[docs]def write_shp(G, outdir): """Writes a networkx.DiGraph to two shapefiles, edges and nodes. Nodes and edges are expected to have a Well Known Binary (Wkb) or Well Known Text (Wkt) key in order to generate geometries. Also acceptable are nodes with a numeric tuple key (x,y). "The Esri Shapefile or simply a shapefile is a popular geospatial vector data format for geographic information systems software [1]_." Parameters ---------- outdir : directory path Output directory for the two shapefiles. Returns ------- None Examples -------- nx.write_shp(digraph, '/shapefiles') # doctest +SKIP References ---------- .. [1] http://en.wikipedia.org/wiki/Shapefile """ try: from osgeo import ogr except ImportError: raise ImportError("write_shp requires OGR: http://www.gdal.org/") # easier to debug in python if ogr throws exceptions ogr.UseExceptions() def netgeometry(key, data): if 'Wkb' in data: geom = ogr.CreateGeometryFromWkb(data['Wkb']) elif 'Wkt' in data: geom = ogr.CreateGeometryFromWkt(data['Wkt']) elif type(key[0]).__name__ == 'tuple': # edge keys are packed tuples geom = ogr.Geometry(ogr.wkbLineString) _from, _to = key[0], key[1] try: geom.SetPoint(0, *_from) geom.SetPoint(1, *_to) except TypeError: # assume user used tuple of int and choked ogr _ffrom = [float(x) for x in _from] _fto = [float(x) for x in _to] geom.SetPoint(0, *_ffrom) geom.SetPoint(1, *_fto) else: geom = ogr.Geometry(ogr.wkbPoint) try: geom.SetPoint(0, *key) except TypeError: # assume user used tuple of int and choked ogr fkey = [float(x) for x in key] geom.SetPoint(0, *fkey) return geom # Create_feature with new optional attributes arg (should be dict type) def create_feature(geometry, lyr, attributes=None): feature = ogr.Feature(lyr.GetLayerDefn()) feature.SetGeometry(g) if attributes != None: # Loop through attributes, assigning data to each field for field, data in attributes.iteritems(): feature.SetField(field, data) lyr.CreateFeature(feature) feature.Destroy() drv = ogr.GetDriverByName("ESRI Shapefile") shpdir = drv.CreateDataSource(outdir) # delete pre-existing output first otherwise ogr chokes try: shpdir.DeleteLayer("nodes") except: pass nodes = shpdir.CreateLayer("nodes", None, ogr.wkbPoint) for n in G: data = G.node[n] or {} g = netgeometry(n, data) create_feature(g, nodes) try: shpdir.DeleteLayer("edges") except: pass edges = shpdir.CreateLayer("edges", None, ogr.wkbLineString) # New edge attribute write support merged into edge loop fields = {} # storage for field names and their data types attributes = {} # storage for attribute data (indexed by field names) # Conversion dict between python and ogr types OGRTypes = {int: ogr.OFTInteger, str: ogr.OFTString, float: ogr.OFTReal} # Edge loop for e in G.edges(data=True): data = G.get_edge_data(*e) g = netgeometry(e, data) # Loop through attribute data in edges for key, data in e[2].iteritems(): # Reject spatial data not required for attribute table if (key != 'Json' and key != 'Wkt' and key != 'Wkb' and key != 'ShpName'): # For all edges check/add field and data type to fields dict if key not in fields: # Field not in previous edges so add to dict if type(data) in OGRTypes: fields[key] = OGRTypes[type(data)] else: # Data type not supported, default to string (char 80) fields[key] = ogr.OFTString # Create the new field newfield = ogr.FieldDefn(key, fields[key]) edges.CreateField(newfield) # Store the data from new field to dict for CreateLayer() attributes[key] = data else: # Field already exists, add data to dict for CreateLayer() attributes[key] = data # Create the feature with, passing new attribute data create_feature(g, edges, attributes) nodes, edges = None, None # fixture for nose tests
def setup_module(module): from nose import SkipTest try: import ogr except: raise SkipTest("OGR not available")