"""
*********
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) 2004-2015 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):
"""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.
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/")
if not isinstance(path, str):
return
net = nx.DiGraph()
shp = ogr.Open(path)
for lyr in shp:
fields = [x.GetName() for x in lyr.schema]
for f in lyr:
flddata = [f.GetField(f.GetFieldIndex(x)) for x in 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
last = g.GetPointCount() - 1
if simplify:
attributes["Wkb"] = g.ExportToWkb()
attributes["Wkt"] = g.ExportToWkt()
attributes["Json"] = g.ExportToJson()
net.add_edge(g.GetPoint_2D(0), g.GetPoint_2D(last), attributes)
else:
# separate out each segment as individual edge
for i in range(last):
pt1 = g.GetPoint_2D(i)
pt2 = g.GetPoint_2D(i + 1)
segment = ogr.Geometry(ogr.wkbLineString)
segment.AddPoint_2D(pt1[0], pt1[1])
segment.AddPoint_2D(pt2[0], pt2[1])
attributes["Wkb"] = segment.ExportToWkb()
attributes["Wkt"] = segment.ExportToWkt()
attributes["Json"] = segment.ExportToJson()
del segment
net.add_edge(pt1, pt2, attributes)
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.items():
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]
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].items():
# 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")