How to get WFS feature type schema in Python

Question

I need to get all attribute names and all their restrictions of the WFS feature type. The get_schema method of the owslib.wfs WebFeatureService is not working and throwing an error.

Code:

from owslib.wfs import WebFeatureService
wfs = WebFeatureService(url='https://maps.helcom.fi/arcgis/services/MADS/Human_Activities/MapServer/WFSServer', version='2.0.0')
schema = wfs.get_schema('Human_Activities:Dredging_sites_points_36_2')

Error message:

Traceback (most recent call last):
  File "C:\...\test.py", line 14, in <module>
    schema = wfs.get_schema('Human_Activities:Dredging_sites_points_36_2')
  File "C:\...\Lib\site-packages\owslib\feature\__init__.py", line 380, in get_schema
    return get_schema(self.url, typename, self.version, auth=self.auth)
  File "C:\...\Lib\site-packages\owslib\feature\schema.py", line 62, in get_schema
    return _construct_schema(elements, nsmap)
  File "C:\...\Lib\site-packages\owslib\feature\schema.py", line 122, in _construct_schema
    data_type = element.attrib["type"].replace(gml_key + ":", "")
  File "src/lxml/etree.pyx", line 2496, in lxml.etree._Attrib.__getitem__
KeyError: 'type'

The corresponding call for DescribeFeatureType request works fine: https://maps.helcom.fi/arcgis/services/MADS/Human_Activities/MapServer/WFSServer?request=DescribeFeatureType&service=WFS&version=2.0.0&typeNames=Human_Activities:Dredging_sites_points_36_2

What is a problem?

Is there any other way to get WFS feature type schema in Python than using owslib.wfs WebFeatureService get_schema?

Answer 1

Ogrinfo can read the schema despite giving some error. The error comes because GDAL sends first DescribeFeatureType with a TypeNames argument that is listing all the 156 feature types and obviously the command string gets so long that the server denies it. I can't say if owslib tries to do something similar.

ogrinfo WFS:"https://maps.helcom.fi/arcgis/services/MADS/Human_Activities/MapServer/WFSServer" Human_Activities:Dredging_sites_points_36_2 -so
INFO: Open of `WFS:https://maps.helcom.fi/arcgis/services/MADS/Human_Activities/MapServer/WFSServer'
      using driver `WFS' successful.
Metadata:
  TITLE=WFS
ERROR 1: HTTP error code : 404
ERROR 1: Error returned by server : HTTP error code : 404 (0)

Layer name: Human_Activities:Dredging_sites_points_36_2
Metadata:
  TITLE=Dredging_sites_points_36_2
Geometry: Point
Feature Count: 0
Extent: (1060002.744600, 7173177.611800) - (2820680.049400, 9285403.858400)
Layer SRS WKT:
PROJCRS["WGS 84 / Pseudo-Mercator",
    BASEGEOGCRS["WGS 84",
        ENSEMBLE["World Geodetic System 1984 ensemble",
            MEMBER["World Geodetic System 1984 (Transit)"],
            MEMBER["World Geodetic System 1984 (G730)"],
            MEMBER["World Geodetic System 1984 (G873)"],
            MEMBER["World Geodetic System 1984 (G1150)"],
            MEMBER["World Geodetic System 1984 (G1674)"],
            MEMBER["World Geodetic System 1984 (G1762)"],
            MEMBER["World Geodetic System 1984 (G2139)"],
            ELLIPSOID["WGS 84",6378137,298.257223563,
                LENGTHUNIT["metre",1]],
            ENSEMBLEACCURACY[2.0]],
        PRIMEM["Greenwich",0,
            ANGLEUNIT["degree",0.0174532925199433]],
        ID["EPSG",4326]],
    CONVERSION["Popular Visualisation Pseudo-Mercator",
        METHOD["Popular Visualisation Pseudo Mercator",
            ID["EPSG",1024]],
        PARAMETER["Latitude of natural origin",0,
            ANGLEUNIT["degree",0.0174532925199433],
            ID["EPSG",8801]],
        PARAMETER["Longitude of natural origin",0,
            ANGLEUNIT["degree",0.0174532925199433],
            ID["EPSG",8802]],
        PARAMETER["False easting",0,
            LENGTHUNIT["metre",1],
            ID["EPSG",8806]],
        PARAMETER["False northing",0,
            LENGTHUNIT["metre",1],
            ID["EPSG",8807]]],
    CS[Cartesian,2],
        AXIS["easting (X)",east,
            ORDER[1],
            LENGTHUNIT["metre",1]],
        AXIS["northing (Y)",north,
            ORDER[2],
            LENGTHUNIT["metre",1]],
    USAGE[
        SCOPE["Web mapping and visualisation."],
        AREA["World between 85.06┬░S and 85.06┬░N."],
        BBOX[-85.06,-180,85.06,180]],
    ID["EPSG",3857]]
Data axis to CRS axis mapping: 1,2
Geometry Column = Shape
gml_id: String (0.0) NOT NULL
OBJECTID: Integer (0.0)
Dredging_ID: String (50.0)
Deposit_site__Helcom_site_ID_: String (50.0)
Deposit_site_link: String (200.0)
Unique_ID: String (100.0)
Site_name: String (250.0)
Type_of_area_dredged: String (50.0)
Dredging_activity: String (50.0)
Material_dredged: String (100.0)
Year: Real (0.0)
Country: String (50.0)
Sub-basin: String (50.0)
Quality_flag: String (50.0)
dep_geometry: String (50.0)

With Python it is possible to use gdal.VectorInfo instead of the ogrinfo binary https://gdal.org/api/python/osgeo.gdal.html#osgeo.gdal.VectorInfo.