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How to return WKT of entire polygon with shapely?

How many interior and exterior rings can a polygon have in a standard ArcGIS shapefile?Shapely unable to tell if polygon contains pointShapely WKT precision/roundingWhat does EMPTY mean in WKT?Decompose the polygon with polyline insideArcpy Create Polygon Geometry or Shapefile/FeatureLayer from WKTPython shapely difference between two polygonsIntersection between an angle and a polygon (postgreSQL + postGIS or Python2.7 + shapely + psycopg2)Dealing with a hole (or inner ring) at the intersection of two MultiPolygon polygons in Python ShapelyOGR multipolygon with holes model

3

1

Im learning to use shapely and have two shapefiles--forest, and basins. The two shapefiles clearly intersect (basins is completely within forest). But the way I've gone about it only gets the feature at index 0 of each shapefile, which don't intersect. I know where this is taking place in the script, but how do I get the whole polygon shape as wkt instead of just one record? Do I build a list of the wkt geometry one record at a time?

# Basins shapefile to wkt

basins = ogr.Open("data/Basins.shp")

basins_layer = basins.GetLayer(0)

basins_feature = basins_layer.GetFeature(0) # This is the line

# I'm thinking there should probably be a loop here to get the geometry of the whole shapefile

basins_geometry = basins_feature.GetGeometryRef()

basins_wkt = shapely.wkt.loads(basins_geometry.ExportToWkt())

How do I loop through the whole shapefile and build the outer polygon as wkt or is there another function to get the outer boundary of the shapefile? I guess this is called the outer ring. I want wkt of the whole shapefile exterior, rather than the individual polygons that make it up.

python shapefile shapely wkt

share|improve this question

edited Jul 23 '17 at 23:57

Alex R

asked Jul 23 '17 at 21:59

Alex RAlex R

6017

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  If you're using the ogr module you don't need shapely. All of the functionality of shapely is present in ogr.
  
  – sgillies
  Jul 24 '17 at 15:09
  

  
  
  
  

add a comment | 

3

1

Im learning to use shapely and have two shapefiles--forest, and basins. The two shapefiles clearly intersect (basins is completely within forest). But the way I've gone about it only gets the feature at index 0 of each shapefile, which don't intersect. I know where this is taking place in the script, but how do I get the whole polygon shape as wkt instead of just one record? Do I build a list of the wkt geometry one record at a time?

# Basins shapefile to wkt

basins = ogr.Open("data/Basins.shp")

basins_layer = basins.GetLayer(0)

basins_feature = basins_layer.GetFeature(0) # This is the line

# I'm thinking there should probably be a loop here to get the geometry of the whole shapefile

basins_geometry = basins_feature.GetGeometryRef()

basins_wkt = shapely.wkt.loads(basins_geometry.ExportToWkt())

How do I loop through the whole shapefile and build the outer polygon as wkt or is there another function to get the outer boundary of the shapefile? I guess this is called the outer ring. I want wkt of the whole shapefile exterior, rather than the individual polygons that make it up.

python shapefile shapely wkt

share|improve this question

edited Jul 23 '17 at 23:57

Alex R

asked Jul 23 '17 at 21:59

Alex RAlex R

6017

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  If you're using the ogr module you don't need shapely. All of the functionality of shapely is present in ogr.
  
  – sgillies
  Jul 24 '17 at 15:09
  

  
  
  
  

add a comment | 

Im learning to use shapely and have two shapefiles--forest, and basins. The two shapefiles clearly intersect (basins is completely within forest). But the way I've gone about it only gets the feature at index 0 of each shapefile, which don't intersect. I know where this is taking place in the script, but how do I get the whole polygon shape as wkt instead of just one record? Do I build a list of the wkt geometry one record at a time?

# Basins shapefile to wkt

basins = ogr.Open("data/Basins.shp")

basins_layer = basins.GetLayer(0)

basins_feature = basins_layer.GetFeature(0) # This is the line

# I'm thinking there should probably be a loop here to get the geometry of the whole shapefile

basins_geometry = basins_feature.GetGeometryRef()

basins_wkt = shapely.wkt.loads(basins_geometry.ExportToWkt())

How do I loop through the whole shapefile and build the outer polygon as wkt or is there another function to get the outer boundary of the shapefile? I guess this is called the outer ring. I want wkt of the whole shapefile exterior, rather than the individual polygons that make it up.

python shapefile shapely wkt

share|improve this question

edited Jul 23 '17 at 23:57

Alex R

asked Jul 23 '17 at 21:59

Alex RAlex R

6017

# Basins shapefile to wkt

basins = ogr.Open("data/Basins.shp")

basins_layer = basins.GetLayer(0)

basins_feature = basins_layer.GetFeature(0) # This is the line

# I'm thinking there should probably be a loop here to get the geometry of the whole shapefile

basins_geometry = basins_feature.GetGeometryRef()

basins_wkt = shapely.wkt.loads(basins_geometry.ExportToWkt())

share|improve this question

edited Jul 23 '17 at 23:57

Alex R

asked Jul 23 '17 at 21:59

Alex RAlex R

6017

share|improve this question

edited Jul 23 '17 at 23:57

Alex R

asked Jul 23 '17 at 21:59

Alex RAlex R

6017

asked Jul 23 '17 at 21:59

Alex RAlex R

6017

asked Jul 23 '17 at 21:59

Alex RAlex R

6017

2 Answers
2

active

oldest

votes

4

To get wkt outer ring of a polygon with shapely, you can use next code with your particular paths:

import fiona

from shapely.geometry import shape, LineString



path = '/home/zeito/pyqgis_data/polygon1.shp' #polygon with only one feature



c = fiona.open(path)



collection = [ shape(item['geometry']) for item in c ]



rings = [ LineString(pol.exterior.coords).wkt for pol in collection ]



print rings[0] #0 because polygon has only one feature (one outer ring)

After running above code at Python Console, for my particular path, I got:

LINESTRING (389535.8208391897 4448641.082016046, 397951.9055779715
4459595.351041127, 418925.3231016023 4456522.812168239, 425070.4008473795 4441160.117803795, 412513.0680625305 4427801.253139063, 392341.1824187837 4435148.628704665, 389535.8208391897 4448641.082016046)

By using QuickWKT plugin of QGIS, it can be observed that it works as expected:

Editing Note:

If you have issues to install fiona, an alternative code, by using ogr python module, is the following:

from osgeo import ogr

from shapely.wkt import loads

from shapely.geometry import LineString



path = '/home/zeito/pyqgis_data/polygon1.shp'



basins = ogr.Open(path)



layer = basins.GetLayer()



geoms = []



for feature in layer:

    geom = feature.GetGeometryRef()

    geoms.append(geom.ExportToWkt())



pol = loads(geoms[0])



print LineString(pol.exterior.coords).wkt

It produces same result that first code.

share|improve this answer

edited Jul 24 '17 at 22:39

answered Jul 24 '17 at 0:58

xunilkxunilk

14.8k31842

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  This is very close to what I suggest: iterate over all records in the shapefile as above, get the individual polygon geometries, and make a multipolygon geometry from them. You can then compare this multipolygon to other geometries or dissolve it into a single polygon using the unary_union function.
  
  – sgillies
  Jul 24 '17 at 15:13
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Thanks. This looks like a good solution and I've been trying all day to get Fiona to no avail. I've been able to successfully install it using pip, but can't import it in python.
  
  – Alex R
  Jul 24 '17 at 18:56
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  As you have issues to install fiona, I modified my first code to obtain same result (see my Editing Note) but, by using org python module.
  
  – xunilk
  Jul 24 '17 at 22:42
  

  
  
  
  

add a comment | 

0

You can just use .wkt as wkt_polygon = ShapelyPolygon(..).wkt

share

answered 1 min ago

AtihskaAtihska

1246

add a comment | 

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4

To get wkt outer ring of a polygon with shapely, you can use next code with your particular paths:

import fiona

from shapely.geometry import shape, LineString



path = '/home/zeito/pyqgis_data/polygon1.shp' #polygon with only one feature



c = fiona.open(path)



collection = [ shape(item['geometry']) for item in c ]



rings = [ LineString(pol.exterior.coords).wkt for pol in collection ]



print rings[0] #0 because polygon has only one feature (one outer ring)

After running above code at Python Console, for my particular path, I got:

LINESTRING (389535.8208391897 4448641.082016046, 397951.9055779715
4459595.351041127, 418925.3231016023 4456522.812168239, 425070.4008473795 4441160.117803795, 412513.0680625305 4427801.253139063, 392341.1824187837 4435148.628704665, 389535.8208391897 4448641.082016046)

By using QuickWKT plugin of QGIS, it can be observed that it works as expected:

Editing Note:

If you have issues to install fiona, an alternative code, by using ogr python module, is the following:

from osgeo import ogr

from shapely.wkt import loads

from shapely.geometry import LineString



path = '/home/zeito/pyqgis_data/polygon1.shp'



basins = ogr.Open(path)



layer = basins.GetLayer()



geoms = []



for feature in layer:

    geom = feature.GetGeometryRef()

    geoms.append(geom.ExportToWkt())



pol = loads(geoms[0])



print LineString(pol.exterior.coords).wkt

It produces same result that first code.

share|improve this answer

edited Jul 24 '17 at 22:39

answered Jul 24 '17 at 0:58

xunilkxunilk

14.8k31842

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  This is very close to what I suggest: iterate over all records in the shapefile as above, get the individual polygon geometries, and make a multipolygon geometry from them. You can then compare this multipolygon to other geometries or dissolve it into a single polygon using the unary_union function.
  
  – sgillies
  Jul 24 '17 at 15:13
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Thanks. This looks like a good solution and I've been trying all day to get Fiona to no avail. I've been able to successfully install it using pip, but can't import it in python.
  
  – Alex R
  Jul 24 '17 at 18:56
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  As you have issues to install fiona, I modified my first code to obtain same result (see my Editing Note) but, by using org python module.
  
  – xunilk
  Jul 24 '17 at 22:42
  

  
  
  
  

add a comment | 

4

To get wkt outer ring of a polygon with shapely, you can use next code with your particular paths:

import fiona

from shapely.geometry import shape, LineString



path = '/home/zeito/pyqgis_data/polygon1.shp' #polygon with only one feature



c = fiona.open(path)



collection = [ shape(item['geometry']) for item in c ]



rings = [ LineString(pol.exterior.coords).wkt for pol in collection ]



print rings[0] #0 because polygon has only one feature (one outer ring)

After running above code at Python Console, for my particular path, I got:

LINESTRING (389535.8208391897 4448641.082016046, 397951.9055779715
4459595.351041127, 418925.3231016023 4456522.812168239, 425070.4008473795 4441160.117803795, 412513.0680625305 4427801.253139063, 392341.1824187837 4435148.628704665, 389535.8208391897 4448641.082016046)

By using QuickWKT plugin of QGIS, it can be observed that it works as expected:

Editing Note:

If you have issues to install fiona, an alternative code, by using ogr python module, is the following:

from osgeo import ogr

from shapely.wkt import loads

from shapely.geometry import LineString



path = '/home/zeito/pyqgis_data/polygon1.shp'



basins = ogr.Open(path)



layer = basins.GetLayer()



geoms = []



for feature in layer:

    geom = feature.GetGeometryRef()

    geoms.append(geom.ExportToWkt())



pol = loads(geoms[0])



print LineString(pol.exterior.coords).wkt

It produces same result that first code.

share|improve this answer

edited Jul 24 '17 at 22:39

answered Jul 24 '17 at 0:58

xunilkxunilk

14.8k31842

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  This is very close to what I suggest: iterate over all records in the shapefile as above, get the individual polygon geometries, and make a multipolygon geometry from them. You can then compare this multipolygon to other geometries or dissolve it into a single polygon using the unary_union function.
  
  – sgillies
  Jul 24 '17 at 15:13
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Thanks. This looks like a good solution and I've been trying all day to get Fiona to no avail. I've been able to successfully install it using pip, but can't import it in python.
  
  – Alex R
  Jul 24 '17 at 18:56
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  As you have issues to install fiona, I modified my first code to obtain same result (see my Editing Note) but, by using org python module.
  
  – xunilk
  Jul 24 '17 at 22:42
  

  
  
  
  

add a comment | 

To get wkt outer ring of a polygon with shapely, you can use next code with your particular paths:

import fiona

from shapely.geometry import shape, LineString



path = '/home/zeito/pyqgis_data/polygon1.shp' #polygon with only one feature



c = fiona.open(path)



collection = [ shape(item['geometry']) for item in c ]



rings = [ LineString(pol.exterior.coords).wkt for pol in collection ]



print rings[0] #0 because polygon has only one feature (one outer ring)

After running above code at Python Console, for my particular path, I got:

LINESTRING (389535.8208391897 4448641.082016046, 397951.9055779715
4459595.351041127, 418925.3231016023 4456522.812168239, 425070.4008473795 4441160.117803795, 412513.0680625305 4427801.253139063, 392341.1824187837 4435148.628704665, 389535.8208391897 4448641.082016046)

By using QuickWKT plugin of QGIS, it can be observed that it works as expected:

Editing Note:

If you have issues to install fiona, an alternative code, by using ogr python module, is the following:

from osgeo import ogr

from shapely.wkt import loads

from shapely.geometry import LineString



path = '/home/zeito/pyqgis_data/polygon1.shp'



basins = ogr.Open(path)



layer = basins.GetLayer()



geoms = []



for feature in layer:

    geom = feature.GetGeometryRef()

    geoms.append(geom.ExportToWkt())



pol = loads(geoms[0])



print LineString(pol.exterior.coords).wkt

It produces same result that first code.

share|improve this answer

edited Jul 24 '17 at 22:39

answered Jul 24 '17 at 0:58

xunilkxunilk

14.8k31842

import fiona

from shapely.geometry import shape, LineString



path = '/home/zeito/pyqgis_data/polygon1.shp' #polygon with only one feature



c = fiona.open(path)



collection = [ shape(item['geometry']) for item in c ]



rings = [ LineString(pol.exterior.coords).wkt for pol in collection ]



print rings[0] #0 because polygon has only one feature (one outer ring)

from osgeo import ogr

from shapely.wkt import loads

from shapely.geometry import LineString



path = '/home/zeito/pyqgis_data/polygon1.shp'



basins = ogr.Open(path)



layer = basins.GetLayer()



geoms = []



for feature in layer:

    geom = feature.GetGeometryRef()

    geoms.append(geom.ExportToWkt())



pol = loads(geoms[0])



print LineString(pol.exterior.coords).wkt

share|improve this answer

edited Jul 24 '17 at 22:39

answered Jul 24 '17 at 0:58

xunilkxunilk

14.8k31842

answered Jul 24 '17 at 0:58

xunilkxunilk

14.8k31842

answered Jul 24 '17 at 0:58

xunilkxunilk

14.8k31842

0

You can just use .wkt as wkt_polygon = ShapelyPolygon(..).wkt

share

answered 1 min ago

AtihskaAtihska

1246

add a comment | 

0

You can just use .wkt as wkt_polygon = ShapelyPolygon(..).wkt

share

answered 1 min ago

AtihskaAtihska

1246

add a comment | 

You can just use .wkt as wkt_polygon = ShapelyPolygon(..).wkt

share

answered 1 min ago

AtihskaAtihska

1246

share

answered 1 min ago

AtihskaAtihska

1246

answered 1 min ago

AtihskaAtihska

1246

answered 1 min ago

AtihskaAtihska

1246