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Source code for networkx.readwrite.nx_shp


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 https://en.wikipedia.org/wiki/Shapefile for additional information.
#    Copyright (C) 2004-2019 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, simplify=True, geom_attrs=True, strict=True): """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. simplify: bool If True, simplify line geometries to start and end coordinates. If False, and line feature geometry has multiple segments, the non-geometric attributes for that feature will be repeated for each edge comprising that feature. geom_attrs: bool If True, include the Wkb, Wkt and Json geometry attributes with each edge. NOTE: if these attributes are available, write_shp will use them to write the geometry. If nodes store the underlying coordinates for the edge geometry as well (as they do when they are read via this method) and they change, your geomety will be out of sync. strict: bool If True, raise NetworkXError when feature geometry is missing or GeometryType is not supported. If False, silently ignore missing or unsupported geometry in features. Returns ------- G : NetworkX graph Raises ------ ImportError If ogr module is not available. RuntimeError If file cannot be open or read. NetworkXError If strict=True and feature is missing geometry or GeometryType is not supported. Examples -------- >>> G=nx.read_shp('test.shp') # doctest: +SKIP References ---------- .. [1] https://en.wikipedia.org/wiki/Shapefile """ try: from osgeo import ogr except ImportError: raise ImportError("read_shp requires OGR: http://www.gdal.org/") if not isinstance(path, str): return net = nx.DiGraph() shp = ogr.Open(path) if shp is None: raise RuntimeError("Unable to open {}".format(path)) for lyr in shp: fields = [x.GetName() for x in lyr.schema] for f in lyr: g = f.geometry() if g is None: if strict: raise nx.NetworkXError("Bad data: feature missing geometry") else: continue flddata = [f.GetField(f.GetFieldIndex(x)) for x in fields] attributes = dict(zip(fields, flddata)) attributes["ShpName"] = lyr.GetName() # Note: Using layer level geometry type if g.GetGeometryType() == ogr.wkbPoint: net.add_node((g.GetPoint_2D(0)), **attributes) elif g.GetGeometryType() in (ogr.wkbLineString, ogr.wkbMultiLineString): for edge in edges_from_line(g, attributes, simplify, geom_attrs): e1, e2, attr = edge net.add_edge(e1, e2) net[e1][e2].update(attr) else: if strict: raise nx.NetworkXError("GeometryType {} not supported". format(g.GetGeometryType())) return net
def edges_from_line(geom, attrs, simplify=True, geom_attrs=True): """ Generate edges for each line in geom Written as a helper for read_shp Parameters ---------- geom: ogr line geometry To be converted into an edge or edges attrs: dict Attributes to be associated with all geoms simplify: bool If True, simplify the line as in read_shp geom_attrs: bool If True, add geom attributes to edge as in read_shp Returns ------- edges: generator of edges each edge is a tuple of form (node1_coord, node2_coord, attribute_dict) suitable for expanding into a networkx Graph add_edge call """ try: from osgeo import ogr except ImportError: raise ImportError("edges_from_line requires OGR: http://www.gdal.org/") if geom.GetGeometryType() == ogr.wkbLineString: if simplify: edge_attrs = attrs.copy() last = geom.GetPointCount() - 1 if geom_attrs: edge_attrs["Wkb"] = geom.ExportToWkb() edge_attrs["Wkt"] = geom.ExportToWkt() edge_attrs["Json"] = geom.ExportToJson() yield (geom.GetPoint_2D(0), geom.GetPoint_2D(last), edge_attrs) else: for i in range(0, geom.GetPointCount() - 1): pt1 = geom.GetPoint_2D(i) pt2 = geom.GetPoint_2D(i + 1) edge_attrs = attrs.copy() if geom_attrs: segment = ogr.Geometry(ogr.wkbLineString) segment.AddPoint_2D(pt1[0], pt1[1]) segment.AddPoint_2D(pt2[0], pt2[1]) edge_attrs["Wkb"] = segment.ExportToWkb() edge_attrs["Wkt"] = segment.ExportToWkt() edge_attrs["Json"] = segment.ExportToJson() del segment yield (pt1, pt2, edge_attrs) elif geom.GetGeometryType() == ogr.wkbMultiLineString: for i in range(geom.GetGeometryCount()): geom_i = geom.GetGeometryRef(i) for edge in edges_from_line(geom_i, attrs, simplify, geom_attrs): yield edge
[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] https://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 is not None: # Loop through attributes, assigning data to each field for field, data in attributes.items(): feature.SetField(field, data) lyr.CreateFeature(feature) feature.Destroy() # Conversion dict between python and ogr types OGRTypes = {int: ogr.OFTInteger, str: ogr.OFTString, float: ogr.OFTReal} # Check/add fields from attribute data to Shapefile layers def add_fields_to_layer(key, value, fields, layer): # Field not in previous edges so add to dict if type(value) in OGRTypes: fields[key] = OGRTypes[type(value)] else: # Data type not supported, default to string (char 80) fields[key] = ogr.OFTString # Create the new field newfield = ogr.FieldDefn(key, fields[key]) layer.CreateField(newfield) 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) # Storage for node field names and their data types node_fields = {} def create_attributes(data, fields, layer): attributes = {} # storage for attribute data (indexed by field names) for key, value in data.items(): # Reject spatial data not required for attribute table if (key != 'Json' and key != 'Wkt' and key != 'Wkb' and key != 'ShpName'): # Check/add field and data type to fields dict if key not in fields: add_fields_to_layer(key, value, fields, layer) # Store the data from new field to dict for CreateLayer() attributes[key] = value return attributes, layer for n in G: data = G.nodes[n] g = netgeometry(n, data) attributes, nodes = create_attributes(data, node_fields, nodes) create_feature(g, nodes, attributes) try: shpdir.DeleteLayer("edges") except: pass edges = shpdir.CreateLayer("edges", None, ogr.wkbLineString) # New edge attribute write support merged into edge loop edge_fields = {} # storage for field names and their data types for e in G.edges(data=True): data = G.get_edge_data(*e) g = netgeometry(e, data) attributes, edges = create_attributes(e[2], edge_fields, edges) 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")